How realistic is it to find a freight boxcar with its sliding door open in the US?

I'm trying to write a realistic scene set in the United States and was wondering how plausible this would be.

Imagine someone near a freight yard or rail line finds a boxcar with its large sliding side door partially or fully open. The car appears to be empty, and they climb inside and end up traveling with the freight train.

Does this ever happen in real life? Are boxcars ever left with their sliding doors open while waiting in a yard? Would it be plausible for a boxcar with an open door to end up moving as part of a freight train, or would that be extremely unusual?

I'm interested in both modern-day America and more recent historical periods, including the era when hobos commonly rode freight trains. I'm not necessarily looking for a specific time period; I just want to know whether this kind of scenario is realistic in either setting.

I'd appreciate any insights from railroad workers, railfans, or anyone familiar with freight operations or the history of freight hopping.