After sunrocket went out of business, I missed my chance to transfer the old number.
Now I have realized that I probably would want it back...
Is there a way to find out which phone provider reserved this particular number?
Maybe there's still a chance to reclaim this number?

frosh

What's the area code and exchange (i.e. area code + next 3 digits) of the number? With that you can typically lookup who the originally assigned carrier is/was. (Sometimes you also need to look at the first digit of the last 4 numbers). So if your number was 555-111-2222, with 555-111-2xxx, that's enough detail to lookup who the original carrier was.

Have you called the number to see if it's disconnected? If it's not, it's probably been assigned to a new owner.

If it's been assigned to a new owner, can the original owner reclaim that number?

If the new owner was legitimately assigned the number, it's theirs. If they're willing to give it up so that you (the former owner) can try to claim it, then you may be able to get it back.

If the number was improperly assigned to the new owner, and if it can be demonstrated as such, the original owner should get it back. An example of how such a situation occurs is when an owner ports away a phone number originally assigned to them by a VoIP provider, where after the port has completed, the VoIP provider cancels that person's account but fails to purge the number from their pool of "available numbers." Along comes a new customer who signs up for service w/ the VoIP provider, and they hand the new customer a number which has already been ported out. The new customer is able to dial out under the assigned number, but incoming calls (from the regular public switched telephone network) ring on the real owner's end. Incoming calls from others on the same VoIP network, however, ring on the new owner's end. In this situation, the real owner typically starts receiving calls from friends/family of the new owner (i.e. people who are strangers to the real owner). Such a conversation may go something this:

Stranger: "Hi [new owner], this is [stranger] calling you back."
Real owner: "Huh? Who are you?"
Stranger: "What do you mean? You called me, and I'm calling you back."
Real owner: "I never called you."
Stranger: "I have it right here in my caller-id box, incoming call from 1-xxx-xxx-xxxx."
Real owner: "That's my number, but I never called you. Hmmm"
Stranger: "Hmmm. I'm anyway looking for [new owner]."

Next stranger calls new owner on new owner's cell and tells him/her what happened. At that point new owner calls his/her newly assigned phone number from his/her cell phone and ends up reaching real owner. During that conversation, the common link between real owner and new owner somehow gets revealed: VoIP provider XYZ. Thereafter the mystery (more or less) gets solved. The appropriate solution at that point is for new owner to inform VoIP provider XYZ of what happened, for real owner to call up same VoIP provider to remind them that he/she ported the number away, and for VoIP provider XYZ to re-assign new owner a new number as well as purge real owner's number from their system once and for all. Got it?

too funny, LOL

it seems not reassigned, but 'where' could I look it up?

Basically when a number is disconnected it goes back into a number pool. Phone companies buy blocks of numbers and usually assign all numbers in that block before going to the next one. Back in the day (before LNP) prefixes where exclusive to specific companies. Now it just depends on what company purchased the block. If you call your provider they should be able to let you know if they own or who does own your number. Prefix look up will also tell you what company last purchased the number, but that is not necessarily the company that owns it now.

Oh great, Level 3 communications (former broadwing) owns it now, god knows if they'll give it up.
They probably want to keep entire blocks assigned for commercial purpose.
Thanks, Diggler and slowdive

frosh

If it was previously w/ SR, Level3 was one of SR's carriers. Teleblend has taken over SR's network, so they may have the number at this point. Teleblend, however, is getting absolutely hammered on BroadBandReports.com on multiple fronts: major service failures, extreme lack of customer support, billing issues, number slamming, massive layoffs, etc. They may not even be accepting new sign-ups at this time, but if they are, and if they can give you your number back, sign-up then immediately port your number to a stable provider. Once ported, cancel your Teleblend service.

You can also try your luck signing up w/ a provider who uses Level3 as a carrier and then submit an LNP through them. You'll likely have to come up w/ a phone bill that shows the number is yours though.

look at that :
TeleBlend is still accepting signups from former SunRocket customers! Signup online today to ensure retention of your current phone number. We will work with our carriers to restore your service as quickly as possible. Outbound calling can be activated within a couple of days, but inbound calling functionality, in some cases, could take up to 20 business days since we have to port the number in from your current provider.

I'll give it a shot...

Thanks Diggler!

frosh