all game items lost when switching from snapshot world to 1.7.10 pre-release 4

invalid, downgrading isn't supported

Make separate snapshot and normal minecraft directories, this also prevents Minecraft from messing your normal worlds up when playing with snapshots.

Please see MC-45009. Downgrading is not supported and may cause unwanted errors.

Duplicate ofMC-45009 – If you have not, please use the search function in the future, to see if your bug has already been submitted.