I've had larger knives - Gen 1 Endura, Military, work their way out of the pocket when seated because the knife was long enough to get pushed up, and the clip/handle lacked sufficient entrapment to prevent it. They've hit the floor in the office, slid under car seats, etc. I solved it the first time by checking each and every time I got up, not too cool when discreet carry is needed.
The second thing was to buy a knife that will not do that - my EDC now has a cut back in the Ti frame and a long stop pin in the blade that are actually less than smooth on the draw - but I'm not a knifeslinger, so I don't need a quick draw against someone else. I just want to keep from losing it, and it is secure enough to do that. I accept the tradeoff.
The second thing was to buy a knife that will not do that - my EDC now has a cut back in the Ti frame and a long stop pin in the blade that are actually less than smooth on the draw - but I'm not a knifeslinger, so I don't need a quick draw against someone else. I just want to keep from losing it, and it is secure enough to do that. I accept the tradeoff.