I have a remote drive stack on a HBA card. In this stack is a drive in a single drive pool. If I have the drive out and power it back on, Truenas sees it and displays the connection on the console, However, the pool shows disconnected until I reboot Truenas. Should it not auto detect that the pool is available and refresh the gui?
What you are describing is normal. When you bootstrap the TrueNAS system it will attempt to mount your drives. If any are missing then the pool becomes degraded/disconnected.
Instead of rebooting you could try to import the pool manually but I don’t know of anything which does it automatically. I guess you could create a script that runs and if it senses the drive come back, it could try to import the pool.
It isn’t what you wanted to hear and if someone else has better advice, they will chime in.