How to fix your loadout:
If one step doesn't work go on to the next one.
(keep revisiting your resupply closet)
1. Open your loadout menu click OK on all of the pop-ups.
2. Open your loadout again, it should then make all of your selected weapons default, so select what you want.
3. If you still don't have your items, restart TF2.
How to fix your backpack:
(This is to get into your actual backpack in-order to craft or open crates.)
1. Visit the Mann Co. Store (It shouldn't open on the first time) Click the Store again. (It should open on the second.)
2. Open your backpack.
Opening the Mann Co. Store might also fix your loadout, I haven't tested it yet.