Three is pretty old to not be potty trained during the day, #1 or #2. He might have a bladder infection. Got so busy that he forgot to go to the bathroom.
Suggestions: 1) a reward chart with stickers. Every time he goes potty 1 or 2, give him a sticker. After a week of doing this, every time he forgets to use the potty and uses his pull-ups/diaper/etc. take a sticker away. So many stickers gets him a favorite activity or a new book, etc.
2) No more pull-up/diapers during the day. This will mean more work for you with wet/soiled pants, but the awareness level will increase as well as the discomfort for him... prompting him to change his behaviors. Cause and effect. Cotton training pants and pull up sweat pants, so he can run to the potty and take care of business when he's at home. Again, stickers for every success!!! Praise for near-misses, he's trying.
Night time training works about the same way. Limit the amount of fluid intake about 2 hours prior to bedtime. Make sure he goes to the bathroom before he goes to bed and that he truly voids out. You may want to get him up in the middle of the night to help him be successful. Rubber sheet (flannel covered) on his bed to minimize the laundry issues. It's work, but it works a lot quicker than pull-ups because they get the reality of the situation, where a pull-up just postpones the inevitible, no real consequences for the behavior.
Wish you all well.