I suggest you still keep your save file with most of the progress. I know it feels terrible to lose everything after you've worked so hard for it.
However, if you have a lot of time and very curious, you can make a second separate "main save" by continuing before the infiltration, gifting Scar lots of home-made dinners (make sure you include Tank and give your portion of the food if he asks for seconds). After spoiling them with food, you can now continue on infiltrating the mansion until Redwood Forest is unlocked and progress from there. See how much you'll like this second save file.
Edit: (I deleted this part of the comment, I just realized it's wrong to even suggest cheating)