I personnally tested my urls on the claim form and it worked. If you are getting a 404 error it could be that your url is made up. All instawallet urls that have received transactions are in the database.
Hi Boussac,
I get a 404 on all three previously valid Instawallet URLs I have.
I happen to have a screenshot of the one with the most BTC in, dated not long before the incident occurred, so I know for a fact that the wallet URL was valid and had an above-zero balance of 1.2725 BTC. OK, this might be small beans compared to some other claimants, but it's still my money and I'd like to claim it back. I can also show that in the blockchain that its public address received funds over a period of time:
