Hi there!
Since the 1.6.8 update, Phoenix Linden automated a system to return any inventory that might have got stuck in limbo in our database (THANKS PHOENIX!). All residents accounts are being purged and any "lost inventory" should be returning to residents' Lost & Found folder or the original folders the items originated from if they still exist. This particularly refers to those residents who've received messages that their items had been returned to their Lost & Found folder while they were offline. This new process should update all accounts within a week, so if your item has not appeared in any of your folders, give it at least a week.
If you're still having issues finding your lost inventory, feel free to IM me in-world or a Liaison Linden directly since not all residents' lost inventory issues are the same. If you lost inventory during a sim crash, most likely the inventory data will be lost since the data may have been in queue to be backed up on the resident server. Upon crashing, that queue gets wiped clean. At this point, there is no way to retrieves this lost data unfortunately.
A FEW TIPS: It's never a good idea to edit your inventory or object if you're experiencing lag in your area, always name ALL the parts/prims of your object AND if a particular build/project is that important, do make backup copies =)
Again, always file a bug report with the best repro you can provide. This will help us narrow down what exactly the issue may be. If you have a situation that is not reproduceable, at least describe when/where/what exactly you were doing when you discovered your issue. More information is better than none. Also, please title your bugs reports clearly so that we may locate and manage your issue appropriately. Do keep in mind that creating a bug report or making several bug reports for the same issue will NOT necessarily get you immediate assistance. For that, please contact a Liaison Linden or call Customer Service at 800.860.6990.
Thank you for your patience regarding this matter =)
Kona Linden