That's the surveys providers problem not handouts mods problem, Since you have the proof just go back to the survey thingy and click the help button and you should be able to send in your proof so they can give you the coins.

So i got enough for usp blueprint mw and i sent the trade for it and then i tried to change the offer expecting it to send back my coins when it got canceled (trust me i been on this site for a long time it sent back my coins last time) but it got canceled and my coins didn't come back and i didn't even get the usp any help please?