Why is my phone forgetting the password I know I never changed?

I have had this phone and it did this once before when I was a kid. But last time it didn’t have a password than suddenly it added one..

But the difference is, I haven’t used it for a super log time due to not having the cord for it, but after waiting and wanting to check it out. It won’t accept the password I gave it. SUPER EASY TOO… 2500, and if it’s not that. Last 4 digits of my number. But no, now I’m disabled on my 9th attempt and I’m scared to lose all my childhood videos on it…

Please tell me what’s the deal with this.