Why don't you go back and ask for a convenient time for you to collect your payment. It used to stress me out but now I tend to just write it off and move on. Imagine what they would say if their pay cheque wasn't there at the end of the month.
I once had a customer who said he wasn't going to pay as he had no proof I had been, I told him I had posted a slip and would continue to return until I was paid. Knowing he wouldn't answer the door I had prepared a tiny sliver of bamboo cane, as I knocked I inserted the sliver deep into hi Yale lock. A couple of days later I noticed a piece of plywood had now replaced a glass pane. Result.