I'm afraid this is a difficult one for me to pin down, which is why I've held off on reporting it. However, I've had numerous reports of players whose Time in a Bottles simply disappeared from their inventory, including myself. These have happened frequently enough that I am certain that it's not just a case of misplacing them.

In one case, a player reports that upon exiting and reentering their inventory, the Time in a Bottle transformed into another item (duplicate of an EnderIO Electromagnet that already existed in his inventory), but that's the only report I've had of that, and I cannot verify it personally.

I'm sorry that I don't have any logs to provide, because I cannot pinpoint when the item was lost. Here are my versions:

Minecraft: 1.12.2
Forge: forge-1.12.2-14.23.5.2838-universal
Random Things: RandomThings-MC1.12.2-4.2.7.2

Just wanted to update and say this also occurs with version 4.2.7.3. I'll provide any other information I can, I'm just not sure where to begin. Thanks for your time (no pun intended)!