No, putting the character who founded the guild back in won't help. You have two choices: Either wait until the current guild leader has not logged in for 30 days (AFAIK it's this and not 4 weeks), or subscribe, then you will automatically take the guild from an unsubscribed guild leader (unless the current guild leader is also subscribed).
Going forward, the best way to prevent this is to login regularily and never unsubscribe. Also, if you have a few trustworthy players in the guild make sure they have an officer rang that's above the other members. Then in case you lose the guild leadership, it will transfer to an officer and not a member. Or you just remove everyone who you don't want to become guild leader.
