Missing items after co-op

I hope I'm posting in the right place (I'm quite new to this and to Stardew Valley..) but if not, please remove.
I play on the Switch, primarily single player. I have cabins built for co-op, and a friend visited for 3 in game days. On the 1st day at log in, they were visited by Evelyn at the main farmhouse before starting the day in their cabin. The cabin is positioned next to my Slime Hutch. The main farmhouse, the cabin and the hutch all had/have chests and other decor outside of them.
On the 3rd day, the farmhand ordered a cabin upgrade. We then ended the co-op session (primarily due to the severe lag I experienced hosting, which I now believe was caused by the large amount of outdoor slimes bouncing around my farm- may or may not be related?).
When I logged in as single player on the 4th 'day', I noticed a chest outside the farmhouse was missing. Along with that, an iridium sprinkler, 1 or 2 lightning rods, and most of the chests/items in front of the hutch and cabin. In looking at the pattern of missing items, it would appear all were in the paths of Evelyn or Robin coming thru the farm to their destinations.
I was under the impression the NPCs travel dynamically on the farm to prevent this type of loss, and I was unable to reproduce the issue when upgrading a cabin on my friends farm (playing as the farmhand).
I understand these items are lost to me permanently (which is much more devastating to me than it should be) but I wanted to report this somewhere in the hope that it might be useful to someone.