to be forgotten―pass out of mind―pass out of one's memory―fade from one's memory―escape one's memory―slip one's memory―fall into oblivion―be buried in oblivion
to forget oneself―lose oneself (in admiration)―be lost (in admiration)―be absorbed (in study)―be engrossed (in one's business)―be beside oneself (with joy or grief)
to forget something
消し忘れ
ゆめ忘るな
to carelessly forget to say something
We forgot.
忘れる.
お忘れなく
will never forget