[Zarathustra 1]

I simply ran out of battery and I got locked in bootloader screen when I turned the device back on. I never messed with the OS or anything of the sort. I tried "recovery" and "factory reset" but it just restarts and brings me right back to bootloader.

Should I buy a new one right away or am I missing something?

[B. Diddy]

Welcome to Android Central! You really have a Desire 510? That's a 5 year old phone -- you won't find a truly "new" one.

It sounds like either the firmware got corrupted, or there's a problem with the motherboard. If you just recently bought it, see if it's still under warranty, or if you can return it to the seller. Otherwise, it's probably more cost-effective to look for a new phone.

[Rukbat]

First try charging the battery for 3-4 hours. If the battery is low (and running out of battery does that), Android may not boot properly, so the phone tries to boot Recovery, which may also not boot properly, so it dumps you into the bootloader (which is part of the phone).

If that fixes it, you're still using a 5 year old battery (and buying a "new" one means buying one that's been sitting on the shelf for 5 years, uncharged), so that wouldn't pay. As B. Diddy said, you can buy a lot of new, current phones for under $100 that are better than the 510. (Look for Android Go phones.)