I never check my luggage 3 hours in advance in airports like JFK, MCO, or LAX for international flights as it is theft waiting to happen, and especially when one flies thru CDG, FCO, ATH, or similar ariports. I had our suitcases multiple times "searched" and once "lost." If it is TSA, they always put the note inside but this was other type of searches. In one "search", they had two bags with brand new kids clothes, tags attached, removed. Whenever I had the suitcase delayed, my experience has been that DL was always able to track it down within 24h, if not earlier.
This summer, with my entourage, we arrived at ATH with 12 suitcases (do not ask how 2 adults and a baby managed that and with only paying for 2 extra suitcases charge! long story). Due to various other issues related to our adventure with the AF metal/DL codeshare, the desk agent called the luggage office to have our suitcases transfered to another flight-(yes the computer system in ATH was down for 2 hours and nothing could fly in or out, or rebooked). Conveniently, 2 suitcases were missing. Luckily, I knew someone working there and he personally went downstairs and found the 2 bags hidden and clearly put aside for a "search." On the same trip, at the next airport, I approached the service desk agent who was around the luggage carousel and asked her where I could pick up my luggage from the USA as it had to go through customs. As she was talking to me, she picked up MY newborn car seat that was coming by (it was packed in clear plastic with my name and tag attached and not the saranwrapper thing that they do in Europe ) and was holding it and started leaving. Then I stopped her and asked for the car seat and she started apologizing that she made a mistake and was looking for a customer's delayed luggage. Yea, right. so easy to mistake a suitcase for the car seat.