Item loss bug within Small Bagpack#1199

I put my stuff inside a small Bagpack in Skyblock. Bag was full, I close it ; then thinking that I need my sword, I re-open it, but bag was empty. I tried to deco-reco, to put other items inside (maybe invisible bug) but nothing makes it. Items are lost, and i have no idea why.
I lost my elytra, my sword netherite, my diamond axe, 8 autocrafters, a water bucket, a few electric motors, and some other stuff, but I cannot remember, so nothing important, i guess.
I don’t care the sword (a litle but is ok), etc… but I lost my elytra and that one is quite big loss…