Serpentine belt broke, now missing sensor and wont start

This link had your same problem last comment may help
https://www.cadillacforums.com/forums/cadillac-cts-first-generation-forum-2003/414449-cadillac-starting-problem-after-serpentine-belt.html
This link had your problem and found a solution
https://www.cadillacforums.com/forums/cadillac-cts-first-generation-forum-2003/890066-car-wont-start-after-replacing-serpentine.html

How long does it run? Sure you only changed the serpentine belt? The car would actual even run without the serpentine (or also called accessory belt) since the belt only drives fairly non essential components (AC compressor, alternator, fan, power steering pump. etc).

That broken wire and or part will need to be repaired, may be one in the same for cam positioning sensor and if not working the engine will not start.

it could be your problem for sure ....the senor or wires cut

have crank sensor adjust if not change it

Is it possible the broken belt damaged the crank or cam sensor ?
I can't see a way for the serpentine belt damaging the camshaft.
Was the engine running after the belt broke ?
Have you checked the computer for trouble codes ?

the timing belt is scheduled for replacement at 60K miles, but I dont know why the serpentine belt would break? see if the cam is turning, maybe peek in where you add oil.

The timing belt should not have been affwcted. Sounds like you have everything chk'd and accounted for.. The best way to chk the cam and crank is a compression test.

Does the distributor turn? Some of the old serpentine belt might have got into the timing belt and broke it.