There's a lot of items missing from my in-world inventory

I logged out and back in three times and they were not there.

Clear your cache before you log out the next time. Then log back in and wait for everything to rezz in the direction you are facing when you land in world. Turn 1/4 turn in one direction, wait for every to rezz, turn 1/4 more in same direction, wait......until you complete 360 degrees (it helps if you have the mini map up). Open your inventory. If things are loading great but, if not then, type in the search field the letters A, wait a bit.........B, wait a bit..........so on untill your inventory loads. It might take a while but don't move to a new location until it loads.

If all that fails then the next step is to delete your cache folder manually. To do that, log off again and launch SL but don't log on. Go to the Edit menu > preferrences and on the network tab make a note of where your cache folder is located on your hard drive (it's the box just below the "clear cache" button). Quit SL, navigate to the cache folder on your hard drive and delete it. Try SL again. Do the same slow spin......it will probably take longer for things to rezz this time but be patient. Do the same song and dance with the inventory search if your inventory is not loading.

That is the method I've had success with when my inventory failed to load.

I cant believe that spin around actually works, i waited 3 days of just clearing cache for my items to come back and after i did that spin around today i got it back, just that quick! i am astonished! completely astonished lol! ty for the helpful hint! )