So, I had a guy out for two days and he had about 53 items on him, some rares, etc. I finally got him back today and when I hit collect, I only got about 25 of them. I had 80 Inventory and only 8 taken up. It appears that all of the "rare" items disappeared.
I'm going to test this again, but I think its a pretty dang annoying bug.
Note: I did not click the "coin" button before I "collected" his items.