as per subject, I am stuck in campaign (not loading next scheme) disc ruined?

it is when you loose the helicopter which is supposed to evac you,
I am taken by the water and.. if I really wait a lot then it will come just the start of beginning of next scheme then dark again, the noise coming from the disc is really not normal, seems it is stuck in trying to read some location - this happens only with this game.
I do believe having seen a post of a user claiming a similar problem but in other section of the campaign.

I have carefully cleaned the disc and checked visually, IMHO is scratch-free.

Any idea besides trying to fetch a disc from a friend ?

I answer to myself, solution

1) being a little depressed and from time to time putting the carefully cleaned disc to see if it was loading

2) while waiting, getting a phone call which lasts 45 minutes...

3) ... here it is, loaded the new episode of the campaign ready to pass to next phase

4) being happier and from time to time putting the disc to actually play

I did not monitor the PS3 during the phone call so I could be that it loaded at 30 minutes,
..interestingly no more episode (touching wood) shows this tendency to stuck in the longest loading ever...

so, any other reader landing here for keywords:
disc not loading, disc ruined, stuck in episode, stuck in campaing, blank / black screen

clean the disc and then retry really waiting a lot (>30 minutes)