I had a problem similar to this with a 135 employer who'd I'd worked for for two years. During that time, I saw what happened to every other pilot who left that job, and vowed it wouldn't happen to me. The employer would withold the last paycheck invariably.
I made sure to document every minute I worked during the last few weeks...including obtaining copies of company invoices I'd written students for instruction from those same students.
Sure enough, a month went by without a paycheck, despite repeated calls deflected by the call-screening secretary. I also sent a certified letter to their mailing address (a p.o. box...how convienient for them), which they refused to pick up for three weeks. Still no paycheck ($1300 for the last week of work).
I called the local (un)employment office and asked them how to proceed. They advised me to contact the State Wage & Hour office with a claim. I did, providing extensive documentation of wages owed, per-diem owed, the company's pay structure (the aviation industry often has unusual compensation calculations), and copies of pay stubs from previous weeks' labor and corresponding weekly schedules to corroborate my claim.
I can't say enough about how this office performed. They sent a letter to my previous employer, to which the manager was required to respond. I think my paycheck and the letter they sent both arrived at their respective destinations on the same day, so my efforts may not have been necessary. Neverless, I waited a few days to cash the paycheck just to keep a little pressure on the previous employer. Perhaps they'll be less likely to pull this on the next guy...probably not though.
The lesson...document everything before leaving an employer in this industry. It pays. Perhaps not applicaple in your case, but the experience dealing with this will stay with you.
... just kidding.
