Can antifreeze flow back from the reservoir into the fuel tank?

What is your question?

Would not start. Thought it was the injector module Replace still had the problem. Found antifreeze in the fuel tank. I have no fuel in my antifreeze reservoir or antifreeze in my oil. My mechanic said antifreeze it flowed backward from the reservoir to my fuel tank. Everything I researched is that someone put antifreeze on my fuel tank. Can you confirm.