No Enterprise-B was never lost in battle the only "battle" it was ever seen in was when the Nexus appeared and James T Kirk went missing in truth it's never really stated what happened to Enterprise-B after that i assume the same fate as Enterprise-A she was decommisioned at the end of her service being when the Ambassador class took over the Excelsior class.
I just brushed up on info of Enterprise-B it wasn't lost in a battle but the ship was lost presumed destroyed when the crew reported a unknown infection going around the ship. So it could still very well be drifting through space crewless.