My first LCP (previous version, but model was post-recall) had a "walking" takedown pin. It shifted under recoil during the first range session, not being retained by the wire spring. It happened 2 or 3 times for me in that first and second range session, and also in the hands of someone else shooting it.
I called Ruger and they sent me another takedown pin. (They offered to have the gun returned for inspection, but I asked to just try a new takedown pin, first.) That replacement takedown pin didn't shift under recoil.
Looking at the 2 takedown pins, I could almost see that the first pin's retaining ridge/lip wasn't as prominent as on the second pin. Easy to suspect the round wire spring slipped over the lip under recoil forces. (The wire spring appeared fine, from what I could see, and seemed to have sufficient tension.)
FWIW, I also tried one of those aftermarket takedown pins that have a large slot machined into the body, into which the retaining spring fits (slot head that can be turned to align wire spring inside the pin body's machined slot, and to disassemble the gun). I tried it one time at the range, and the pin actually rotated under recoil so the machined slot no longer held the wire spring, and that pin walked out under recoil, too. I won't be using it again. I'm still using the replacement (second) factory takedown pin Ruger sent me, and it's continued to be fine.
The takedown pin in my second (stainless) LCP has yet to shift or walk, and seems to work as intended.
Unless your buddy knows the previous owner, since it was bought as a used gun there's no real way to know how it was treated or whether anything was "modified" before he bought it. Maybe the previous owner fired some hot-rodded "+P" .380 loads, and something was damaged. Ruger would have to determine whether it was a defect or owner-induced damage in that case.
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