If you messed up on your comment while in the field and you've selected "Done" just select the cache again, select "Go" and re-log your attempt which will give you another opportunity to create a comment.
Later, at your cpu, when accessing your field notes, you will have 2 logs for the same cache - just delete the log not needed.
Keep your comments short and sweet in the field just reminding yourself of the cache experience. You may elaborate later at the cpu...
Capt. Ed (caped)