Even if he can't sign a message from his single BTC wallet I believe he can prove ownership of his account from this thread:
https://bitcointalksearch.org/topic/wts-cheap-hosting-packages-starting-from-015-per-month-1368584You accepted payment from the following currencies: BitCoin, DogeCoin, LiteCoin, ReddCoin, PerfectMoney, Payeer, AdvCash, OkPay, WebMoney, SolidTrustPay, Payoneer, Skrill, Neteller, Paypal and Paxum (buyer cover the fees)
Check your emails from BTCT and contact all the people you dealt with and confirm the payment methods they used so they can vouch for you and I believe if you can provide enough evidence that you were the one providing that service might serve as sufficient evidence the account is yours.
That is something I believe might help your case if you can't sign a message from that wallet.
yeah, true... I offer that services... But i just created a signed message from what wallet and i was about to send a message to the Administrator
If you post it here, the account will be useless for any scam, because you have proven that you own the account. IF you decides to do it, remember to include a date, so it can't be used against you. If you include a date, there isn't going to happen anything bad. Instead it would confirm that you are the right owner.
Good... i will post it here, right in this message.
Yes it is ok to post your sign message here so that we can verified it right now using verifier so that we can know if you are the owner of the address mention here..
i will now...
--------------------------
-----BEGIN BITCOIN SIGNED MESSAGE-----
My account Cosmas has been hacked. Please reset the email to
[email protected] . The current date is September 06, 2016, 06:10:33 PM.
-----BEGIN SIGNATURE-----
1EWDwFd5hAExrf1pF6V7Ff5dGvD23ZgpH1
IO9B0W1zClHv1jDYXsxageR+DYpw9wprqefDqoLDX49NP61akekIbaHRMmMNW19NPNLFogmLnkIoQjaBee5Qfzc=
-----END BITCOIN SIGNED MESSAGE-----