I noticed while opening chests in Sweet Blossom Orchard a message that caught my attention:

[01:46:37 PM] You have found a Treasure Chest. What do you wish to do?
[01:46:38 PM] You interact with the Treasure Chest.
[01:46:38 PM] You have found an item: !
[01:46:38 PM] You have found an item: [Shamrock] x5!

I didn't think too much of it, but then it happened again. At first I thought it might be a bug, but then a thought struck me and I checked my Equipment Tabs, and sure enough they were full; I'm guessing the blank item was a piece of equipment that wasn't able to fit in the full inventory. It would clear up a lot if a little message of clarification was added to the log (and dialogue box) just to clear things up!