I use a baggage belt with a code and put it in between the handle in case it slips off. I have lost it today. When I got it at MLE my belt was missing. I know for a fact that I locked it so unless someone was able to unlock it or cut it off there would have been no way it would have slipped off. The last flight was EK and the other two flights was AC.

If you flew through a US airport - did TSA place a note in your bag that they had searched your bag (I dont know if they are still doing that...)? If yes, maybe they placed the strap inside the bag? Was anything missing out of your bag?

15+ Years Ago, I used ones that locked and ones that just "snapped" into place as extra security protection and b/c one of my folding bags tended to open wide during transit. It was also a handy way to identify my bag in a sea of black bags. Check in agents (Virgini and BA in UK), Delta in the USA, Singapore in Asia and SAA in South Africa would often tell me I have to remove it b/c it could get caught in the bagged machinery. After I lost or lost track of them, I stopped using them (and the wonky folding bag).

Maybe it got caught and broke or a "helpful" handler just cut it and removed it to prevent it from (or when it did) jam some piece of equipment.

I did not pass USA and this was the first time it had gone missing. No there was no strap inside the bag. I did not seem to notice that I have lost anything either. Lots of people have these belts on.

That could be it but I had tightened it very much so there is no loose play at all.

I suspect (assuming the OPs flights passed through US TSA jurisdiction) it was removed by TSA for inspection and not replaced afterward.

If it was TSA approved, it was probably just forgotten. If it was not TSA approved, or if the symbol wasn't obvious, the TSO may have cut the strap off. Either way, there should have been an inspection notice inside the bag when it arrived at its destination.

If the bags didn't pass through TSA jurisdiction, all bets are off.

I know my travels are a small sample size, but I've been using an external strap on my checked bag for about twenty years and never had an issue with the baggage handling equipment. Like OP, mine is one with a TSA lock on the buckle, and I thread it through the bag's side handle and tighten it like a compression strap so there is no way to get anything caught under it.

It's my understanding that baggage handling equipment at US airports is basically conveyor belts with side walls to guide bags through the system. Bags can get stuck, I know that, but I don't believe there are any protrusions inside the system that could get caught on a strap.

After all, if something could get caught under a tightened strap, it could also get caught on a protruding handle.

Now, DANGLING strap ends, that's a different story. You don't want any dangling straps on a checked bag, those could get caught between rollers and under the belts and cause all sorts of backups in the system. I've been told that by airline counter staff a couple of times over the years.

Mine was YYZ to DXB and then to MLE. I got them to check at MLE and they did check the hold and then the baggage sorting area too. I have flown with this strap many times thru YYZ and MLE and had no problems and thus could be DXB. Yes mine was tightened as much as it could and for sure it was not loose and nothing could get in the way as I also got it through the handle and really tighten it again.