OR might I suggest a third possibility? (Though this one might have similar consequences to your second take).
1 - LB's dad really did find an iphone in the park and gave it to her. She used it as her "ipod".
AND
2 - AM's iphone went missing (maybe DM took it?) and DM decided to create another little wedge between people by suggesting maybe LB stole it.
So, DM stole LB's "ipod" and got the serial number off of it. Then he pretended to just "find" her misplaced "ipod" and told her it was AM's. He claimed it had the serial number for AM's missing phone,
but we don't know that this was true, only that DM said it was. See texts starting November 30, 2012 from billandrews timeline for this series of events.
This is something I brought up in
an earlier post as an example of how manipulative DM could be. As I noted there, I am inclined to believe LB's story because she stuck to it during her text exchange with DM on December 8th when he promised to "reward her honesty".
Others have noted how DM played people off against each other. I think this is just another example.
All MOO.