Corrupted Instance bars entry "Disconnected from server"

So I rolled a Twinned Quarantined Quarters of Exposure, managed to kill both the Sunburst Queens inside, but only after it spawned many, many minions inside. Enough to kill my frames. After a while it booted me from the instance and I'm unable to rejoin it due to an error message:

Error: Failed to join instance because: Disconnected from server.

To rub salt in the wound: it had dropped a unique. It's still on the ground in the instance. I'm a little bummed about it.