MRQB wrote:

as a student pilot who busts you and who questions you how do they find out
ect.

The local FAA inspectors bust you. It is typically done either because some
"friend" or vicious FBO complained (the argument usually being that you "took
money away from them" by flying him for less). It can also occur by accident if
an inspector is in the FBO and overhears a chance remark by either you or your
passenger (or sees money change hands). Your chances of the latter are much
reduced on weekends, since few inspectors work weekends (at least in this area).

In short, if you and your passengers keep your mouths completely shut, there's
next to no chance of you getting busted.

George Patterson
God grant me the senility to forget the people I never liked anyway, the
good fortune to run into the ones I like, and the eyesight to tell the
difference.