Years ago, I was renting a house. I wrote all my checks & putthem in my little truck, on the bucket seat next to me. The following weekend the landlord shows up all PO'd because the rent check had not arrived. I was certainly perplexed! He calmed down when I showed him my check register... I wrote him a new check & he went away happy. I put a stop on the check. Months later I discovered the check in the truck behind the seat where it had slipped down between the cushions.
I don't like envolupes... after counting several times... I use a paper clip to keep the bills together & carry them separate from my own funds.