I signed it with my Steam Id 64 (unchangeable profile link).
http://steamcommunity.com/profiles/76561198085699289

I checked your custom url and it doesn't exist.  PM'd you for your steam profile link.

76561198085699289 that was my signature on the transaction.

http://steamrep.com/profiles/76561198085699289
http://i.imgur.com/cs0E0Y2.png

I also leveled up from 30-50 new Screenshot looks like:
http://i.imgur.com/yK2MGuM.jpg