I used a solo extraction portal on Artifact Refinery, then sat back and watched other players in the game for a little while.
After I exited the game I stashed some mats that I extracted with, sold the Ward that I received via the Warden's Eye artifact in the last round, and then realized that all the gear that I had equipped in the previous round had vanished. But all the other stuff (including gear pieces) in my inventory that I extracted with was still there.
#Equipped Gear disappearing after successful extraction
dusty pebble
weary cobalt
Hiya Jadmanthrat 
Ill investigate this issue! Appreciate the report!
paper flume
Can also confirm my last run of the day today had this happen. No unique circumstances or anything. Took a solo extract portal with 6 minutes left on the game timer. Noticed I had 0 gearscore when back in the lobby, but my entire inventory was still full of meds and the loot I picked up.