Recently the Archive has reported on 2 games which, in my view (and I still recall them) had disappointing endings to triumphant evenings - namely winning the 2nd Division (old) title against Queen's Park in 1971 and winning the Glasgow Cup against some other Glasgow team in 1981.
In both instances no post-match victory celebrations occurred. As I recall after the QP game there was actually an announcement which specifically told the fans (almost all of whom had stayed in the ground) to, and I quote "go home!". Whilst at the 1981 game, as reported today - the presentation was made in the tea-room to presumably preclude any reaction from the defeated club's supporters (frankly they probably didn't give a monkey's in any case).
It would be nice to think that such situations, as regards the precluding of the celebration of a PTFC triumph wouldn't happen nowadays (albeit perhaps the probability of any triumph occurring is perhaps less likely).