Lost my valuable items

I had a lot of good stuff on me including 26 ancient debris and a very good diamond pickaxe

i was going back from the nether but for some reason started suffocating when i entered the portal. I lost my stuff and when i respawned it was no where to be seen. Cheats were disabled and i really dont want to switch them on. But i would like that stuff back. Im not sure if this is a proper bug but it has caused a problem. Please check.