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.