This was first encountered when i was in a trial chamber. I fully charged a trident at a pot and threw it. The pot broke and i was unable to find it, effectively losing it. What happened was that i threw it at a very specific angle between the corner of the floor and the wall, causing it to go though the blocks. This can lead to it phasing though entirely, or becoming fully inaccessible.

How to Perform:

1: Create a floor of solid blocks. 

2: Make a wall of solid blocks at the edge of the wall. You should effectively have an edge of a room.

3: Place a pot on the floor directly in front of the wall. You do not have to add any items inside.

4: Fully charge your trident. 

5: Align your cursor (the + that appears) with the intersection of the wall and the floor. Basically the edge of the blocks.

NOTE: Adding a corner (marked with the mangrove planks) does NOT impact this bug.

6: Throw the trident. If performed correctly, the trident will phase through.

Demonstration:

Video.mov