still have my copy shrink wrapped (ps3) although i think im gonna give it a go. Saw this on gamefaqs, but i haven't seen anyone else on, more credible sites seem to confirm this....
 

If your options are set to "Game Type <Single Player>" and you sign out of PSN you will NOT get this glitch. Players using this setting have reported zero save glitch problems. If your settings are set to "Game Type <Cooperative>" and "Game Visibility <Playstation Network>" you have a chance of obtaining this glitch. All four times I've been glitched have occurred while playing under these settings. Players on my friends list and Gamefaqs users in other topics are also posting similar results.
 
Normally when the game auto-saves you'll see small text on the left side of the screen saying "Game Saved." Also note that at the exact same time a biohazard symbol will appear at the top right of your screen showing that the game is indeed saving. This is what you want to see at all times.

Secondly whenever you fulfill the requirements to unlock a trophy you'll see small text on the left side of the screen saying "Trophy Obtained: [name of trophy]." At the same time you'll see said trophy 'ping' on the top right of the screen. This is what you want to see at all times.

No, of you REALLY set it the single player before ever playing the game at all... you don't need to sign out of PSN.

I set it to single player before creating my first character, it was the first thing I did. Not once have I ever had a notification that I could join another person's game or that they were in my area. If you set it to single player before doing ANYTHING else, it will be just like a single player experience, and you won't get any save glitch (25 hours in for me, 0 glitches for me).

I really want to buy this game but I'm terrified of the technical issues.

I don't know if this helps-but I played significant amounts with a friend through coop and never had any save issues. When I played by myself for about 3 hours right before the patch I lost all that progress. The patch also reset ALL of my in progress trophies to 0. So even though I have found a lot of the collectibles-it now says 0 found, which means I will never be able to get it unless they somehow fix it as the collectibles I have already found are not there anymore.

Hearing about all of this game's technical fuck-ups is actually becoming quite interesting.

if there's a vehicle available, you can trigger a save by hopping in the driver's seat.

Beat the game in one sitting. PROBLEM SOLVED!

It really bugs me that there is no save option anywhere, I hate having to rely on checkpoints. I'm so afraid I'm going to get to a part where I am stuck in a wall or something and it is going to checkpoint there.

It's unfortunate so many people seem to be having problems. I haven't had any yet and I'm on PC of all platforms. If the internet is to be believed, my computer should have gone up in flames a while ago.

Beat the game in one sitting. PROBLEM SOLVED!