Alas It's happened to quite a few people. I remember I was -7 on the 9th green(9hole comp) with a 3ft birdie Putt and Banggg, Comp timed out and finished.... Yes I was fuming too...lol
Once the clock runs out that's it... game Over, Sorry.
I always check the time remaining for all comps and I always have a Boost in my bag if I needed to play a comp in Quick time.
-Roger