IF any framing occurred (IMO possible but in the category like everything else in this case of highly unlikely but we’ve already seen stranger things) it would not have knowingly involved A&L as you speculate above nor knowingly involved BG either, but would’ve occurred something like this;
Again MOO thinking way outside the box..
1) L takes short 43-second video of BG, her being spooked/suspicious by his nearby presence on bridge
2) L stops the video when for whatever reason, after a short conversation with the man her fears are relieved
3) A & L voluntarily descend the hill without BG…whether to meet a_shots, seek alternate route to avoid a bridge re-cross, go a different direction than BG is going, or other unbeknownst reason
4) A & L encounter peril at the hill’s bottom - either someone(s) waiting for them to expectedly arrive or they surprise a group conducting other illegal business
5) perp(s) pull L’s phone, examine it, and to their good fortune discover a video in the last hour of a rather unusual encounter near the end of the bridge
6) after perhaps some editing/splicing, they purposefully leave the phone where it will be found - insinuating this guy in the video will be suspect #1
All MOO