DTE detroit edison deposit was -lost? They claimed I never paid a deposit Detroit Michigan

My wife and I moved from west michigan to Inkster, Michigan. We rented an apartment from my uncle and DTE detroit edison required a $250.00 deposit because we had never had an account with DTE. When we moved one year later, our deposit had mysterously disappeared. The woman said we had never paid a deposit. We couldn't find the receipt for the cash we had paid them so.....we were out of luck! My wife thinks that an employee took the money or paid their bill with our money since we paid in cash. How were we going to prove it if we don't have a receipt? She thought, well, they have it on our account so we'll be alright! I had to explain to her that there are alot of scammers and theives in Detroit and not to trust anybody! I bet the woman who took our cash for the deposit took the money, but how do you prove it without a receipt?