One of our players pointed out that he could put any item into a chest minecart and it would not show up in the logs, essentially making it untraceable.
Plugin version 20.0 on a 1.17.1 paper server

This is (related to?) one of the imported BukkitDev issues (#26). It also applies to other minecart variants; for example, CoreProtect doesn't log placement or interactions with chest minecarts, furnace minecarts, and TNT minecarts. This is obviously an issue if you're trying to track item transactions or who exploded a TNT minecart.

So: there's no fix that I'm aware of, but this is inspiration for a new feature which I might look into today.

would love for this be added

Me too