I could have sworn that CBS aired what happened to the Enterprise-E during the half hour timeslot after Big Bang Theory between the transition from Rules of Engagement and Rob.
In that special episode, the Enterprise-E arrived at Starbase 236 and found the Borg. The Ent-E was unable to send a message to Starfleet and began to fight their way past the Borg armada. Suddenly, four Romulan Warbirds decloaked and attacked the Ent-E while it was already engaged with the Borg.
As the lead Warbird was about the fire the killshot, one of the bridge officers pointed out that it was the Ent-E and not the Ent-B. The Romulans hesitated and found themselves engaged with the Borg.
As the Ent-E began to limp away from the battle, a tiny Klingon Bird of Prey decloaks. Their alpha strike is enough to destroy the Ent-E. As the captain of the Bird of Prey begins celebrating with his crew about destroying the Enterprise, they're caught in a tractor beam from a Tac Cube and destroyed.