It seems to be an old bug
I really wander if there is any chance this bug is fixed, I just started 2 days ago and get into this bug, it causes an very bad impression in an game that seems to be great with out this kind of bugs, and it seems to be easy to fix.
I found out lather that there is some ways to workarround this bug, eather using an dead body to colide and throw away the bag from the river out, or to input stuff on the bag until its big enough to be able to be accessible, just if someone else gets into this bug and its not fixed yet you can try this.
Tx