Dory is in search of her family in Finding Dory's first trailer
The poster, released yesterday, said "she just kept swimming." And the opening shot reveals how easy it could be to lose, or be separated from, her.
Dory must have a memory bank deep in reserve where essential information and memories are kept. She remembers the past vividly at times, though she seems to be asleep at the time, and she managed to keep P. Sherman's address in mind when she really had to. Perhaps her desire to meet her long estranged family may be enough to keep her focused and on the straight and narrow.