difficult situation.
How much of oil you had to add? What surprises me, that you did not mention the oil light. It did not turn on?
I don't think that any engine would be capable to work 150 miles with no oil. I think there was some amount of oil, however low level of oil may mean low pressure in oil system and then it may happen that in some places oil will not get, or there will be lower amount of oil - specially I think of the cams. For me this is the place where it is more likely to have additional wear caused by low oil level and you can not diagnose/prove other than physically measure (open the top of engine)
Ticking noise may be the cams, it may be also hydraulic tensioner (if it is in the 250 engine - I don't know this engine), or it may be also anything else.
It is indeed difficult situation. I see two possibilities:
1. the oil light works fine, dipstick was dry but it was still enough for the engine, just the tensioner had not enough pressure (ticking), but if the engine sound is now fine, everything is OK and don't worry
2. the oil light/oil level sensor/oil pressure sensor is damaged and car was running 150 miles with lower level of oil than recommended by manufacturer and this may mean problems. Why electronic oil measurement did not work? Is the car still in the warranty? How is it possible that the seal cracked (did you mean the seal in the screw under the car for draining the oil?) - for me it looks like the garage did not follow the general instructions, which means always new seal when changing oil and following the tightening torques.
I briefly went through the instruction manual and I could not find the rule to check the oil before every drive. Doublecheck this and if it is not there, I would take further action with the garage.