Bambi’s mother was seen in cameos in other Disney films like The Jungle Book where Shere Khan first appears and he’s stalking a deer and then there’s Beauty and the Beast where during the beginning there’s a shot of Bambi’s mother drinking from a river. And for those who argue that these films take place and different locations and times, then explain the House of Mouse TV show where characters of different times and place are all around at the same time(that’s the Disney universe for yah. :P). So this confirms that she ran away to get Bambi used to being on his own as part of growing up, which is why she told him “Don’t look back!” so Bambi doesn’t notice his mother FAKING her death the moment she went offscreen and then told the Great Prince tell Bambi that she can’t be with him anymore. After all, even real life deer mothers seperate from their offspring as they get older. Even Faline wasn’t seen with her mother by the time she was an adult.

^ Hm, interesting. I'll watch that scene again right now.