Razz1 said:

I went to another brother hood and I lost all my troops on the Bastion.

What happened to them?

All my rum production increased  by more than 4 times per hour. I lost all my troops.

How can I get them back?

Hi there!

Let's clarify some details. You've sent your Troops to the Bastion as a reinforcement. I'm afraid you've lost your Troops via the Battle. Please check your battle reports to find the information about your loses.

Unfortunately, we can't refund your Troops if they were lost via regular gameplay, Captain.  

Basically the proof is on you to prove the bastion wasn't attacked and you really did lose your troops magically. I know we've seen troops disappear during raids, so this might be possible but again you do need to prove the bastion wasn't indeed attacked. Something worth noting though, when defending those with the largest fleets tend to lose the most in attacks compared to the guy with substantially less.