I am from Philadelphia and I grew up saying, I forget when trying to recall something unsuccessfully. When I came in contact with people from other states, mostly in the mid-Atlantic region, I heard people say under the same circumstances, I forgot in the past tense. The latter implies that the forgetting happened at a certain point in time in the past, while the former seems to imply that as long as you don't remember, you are continuously forgetting.
Which is the more widely used, and does it break down along regional lines?