Full inventory=new items picked up disappear

I was doing alot of mining, so my inventory was probably full. I found 8 diamonds and an emerald I'd saved for last. I didn't think about clearing room for them, just mined them up (since usually you can't pick up anything when inventory is full). It looked like I had picked them up (I walked around and collected them all), so I took them back to my chest. 1 min later, at the chest, I realized they weren't there. So I went back to make sure I'd picked them up (another minute)... nothing... :'(