It is still there, now with 5 days remaining, I have been on the game daily since I started and iI have not entered another Brotherhood or done anything to delete my brotherhood.
I've notified the Support. To make it easier for them, please write your platform (FB/Plarium), map (s1/The Pirate Bay, s2/The Golden Coast, s3/The Sirens' Strait), and your coords.
I've just heard back from the Support. It seems that you triggered the dismissal of your BH manually. They have now cancelled it, and any future dismissal will depend only on your actions and activity.
No, I have played the various plarium game for some years and I am sure, that I have NOT started a deletion of the the brotherhood, but thank you for your help.
Knowing Plarium, it may have been a glitch, albeit a very weird one. However, just to be safe, maybe change your password, in case someone guessed it and decided to abuse it.