IANAL, but my gut sense is that it would be counter-productive to take any actions which could in any way be construed or framed as harassment or intimidation. Such a thing could come back to bite one on the ass in the unfortunate event that it is necessary to move this through the legal system.
Worse, if the Paymium crew turn out to be the perps and end up on the wrong side of some fellow criminal's actions I personally would want nothing whatsoever to drag me into a now greatly expended investigation.
Hear you, but I am proposing a simple, courteous information gathering visit - no baseball bats! I think it is quite natural to visit the offices of a company that misplaced your money to enquire what is going on. Nothing sinister in that...
Of course. But there is no telling how such a thing might be represented down the line. Or how it might look if some other party decided that it would be effective to play not-so-nice.
This is simply my opinion on the matter and does not mean that it is the right way to proceed. I tend to be cautius about these things and try to anticipate as many future possibilities as I can. I do like to win when I choose to play.