It is technically possible - there is the EPIRB system for surface vessels and the “I’m Dead” ‘rescue buoy’ system for submersibles/submarines. However, I didn’t see anything indicating that the Titan was equipped with either system so I don’t know how they got such a signal either. The only thing I can think of is that they lost contact over what was basically a hydrophone modem system then they got some fragmentary packets indicating system failures - much like some recent air crashes where the aircraft’s online reporting system started sending data indicating disaster shortly before the aircraft was destroyed.
That makes perfect sense, the support ship gets a weird data stream for an instant as sensors go blip for the final time.