Flip-tops typically have a little notch for your finger. If that caught on something while putting it in a bag, there would be more than enough force to open it. I’ll stick to screw tops.
Could be just the lingering trauma of said shampoo bottle a long long time ago.
I do have a subconscious habit of checking that screwed on caps are actually screwed on when putting them away
What about just super gluing the flip top down? You then have a lightweight alcohol specific bottle.
At least your pannier smelled good when the shampoo came undone
