Other thieves have indeed stolen metal from abandoned bridges in recent years... I can think of two standing abandoned pony truss bridge examples right now. There also was a bowstring in storage that thieves took. They were caught in the act and the weight of the truss on their truck foiled their attempt to flee police.
Not sure I can recall any theft of in-service bridges though.
Obviously only the very dumbest and lowest forms of life on this planet would steal metal from a historic bridge for a few bucks of scrap. However taking metal off of a fracture critical type of bridge is beyond stupid since the bridge could collapse while the thieves are on the bridge attempting to steal the parts. Swift justice. Furthermore, if anyone attempting to use the bridge after the theft is killed by a collapse of the bridge then the thieves would likely face negligent manslaughter or something like that and do some hard prison time.
I know the county well, (at least as well as you can get to know a place in a month) but still can't believe anyone would try to scrap an in service bridge.
Have any of you heard of anything of this sort happening to another bridge anywhere else?