Serpentine belt and idler pulley

[Mreddd]

I have 2 Ford trucks and love them. I love this site also. My wife is driving a 98 Taurus 3.0 and this is where I need some help. I changed the alternator out because the old one was wasn't charging enough and drained the battery leaving her on the side of the road late one night. After running it for about 15 minutes making sure it was charging properly, she drove it on the interstate and 5 miles later the idler pulley apparently came loose and caused the belt to break. The bearings on the pulley also came apart. This also broke off 2 wires that connect to a small plastic solenoid or something like that which is bolted next to the crank damper. My questions are: What can this part be? Why would the idler come loose and break if I never touched it (the bolt) coincidence? and will the engine start and run without the belt installed. Can this damage the engine or components? She actually tried to start it and it just turned over before I was able to get to her and have it towed. I appreciate any and all responses. This was suppose to be a dependable car for her to drive to work and now it's got me guessing. Thanks in advance.

[Mreddd]

Well no responses so far but that's cool because I figured it out all by myself. So I willl answer the questions in case someone else has this problem and needs advice. The part that was next to the crank pulley is the crankshaft position sensor. The belt, upon breaking, smacked the wires clean off. This is the reason it wouldn't start. The reason the idler pulley broke was in my best guess, just a coincidence. The bearings were bad and it was an original part. The car can start without the belt but not recommended since the alt. and other parts run off of the belt. That was easy. My advice to anyone that needs an answer quicker....post it under the correct subject and do the research yourself.