Forgotten Banana
If it wasn’t for the title, would you have been able to guess what you’re looking at? We’re betting on no because usually, we throw bananas out as soon as they get a little too brown for comfort. Apparently, this is what one looks like after a significant amount of time passes by.
The OP had put it in his golf bag last summer and forgotten all about it. Once the fruit goes past the squishy and stinky stage, it decomposes and becomes fossilized like this. You learn something new every day. Think about all the ants that may have been inside his bag at some point. Ugh!