Re: Rule 13.6
If a player drops the disc unintentionally (e.g. slipped out of hand while swinging from forehand to a backhand throw) it is a turnover.
The Rule 13.6 was introduced because (my understanding)
1) Earlier players weren’t aware that after turnover (say out of bounds) that the player who picks the discs has to be the thrower. Instead, player near the the disc (where it went outbound) picks the disc and gives it to another player of the same team (like how it is done in football for throw-in). Though players did this because of their ignorance about the rules, this was considered to be turnover. To be fair to them, the player who picked the disc is asked to regain possession and resume the play.
In the case you suggested, the player cannot take advantage of this rule