The movie Prisoners is quite difficult to understand. I am still trying to understand how Joy escaped.
When Joy was in the hospital, it seems that Bob was in her flashback. So did he help her escape?
Do we know where was she found?
The kidnapper Holly Jones mentions that she brought the girls from the underground prison to her house because she was lonely with Alex Jones gone.
Joy's flashback in the hospital indicates that, at some point while they are in the house, Keller Dover shows up for his visit with Holly Jones. Joy and Keller's daughter are both drugged and mostly unconscious, but Joy hears or otherwise senses that Keller is on the property, so that's why she mentions it in the hospital.
Later, the girls somehow managed to make a run for it from the house - but only Joy succeeds in getting away. The flashback shows Joy running through some woods and then arriving at the edge of a freeway, where presumably she was rescued by passers-by.
it seems that Bob was in her flashback.
No he wasn't. Bob had already been arrested and killed himself by the time Joy escaped.
So did he help her escape?
No he didn't.
Instead, Joy and Anna somehow manage to sneak out of the back door of the house.
(We are not shown how exactly. We are merely shown them walking along a wall in the house and towards a door. Given that the flashback shows bottles of the drug, one possibility is that Holly Jones thought she had them thoroughly drugged but made a mistake with the dose.)
However, while Joy gets away, Anna is caught by someone whose back we see:
This someone grabbing Anna must be Holly Jones. It can't be Bob Taylor because Bob had already been arrested and killed himself by this time.
The height also matches. The person grabbing Anna is not much taller than Anna.
Keller (Hugh Jackman) next to Anna:
Keller next to Holly Jones:
Joy manages to run all the way to a road where she is picked up by a passerby as she's running across a road: