Put the summary of the bug you're having here
What I expected to happen was...:
to see a barrier while holding one in my left hand.
What actually happened was...:
nothing.
Steps to Reproduce:
1. Place a barrier
2. Put a barrier in the offhand slot. Do not hold a barrier in the main hand slot, or the glitch won't show up, or "show up."
Something I forgot to mention is that I was, in fact, in creative mode at the time.