How do I get them back in? It's so aggravating not having my mostly used words not in my predictive text anymore. Why have they gone?

Which keyboard/input are you using?

 

If the default, sounds like your user dictionary was corrupted

Yeah just the default one. How would it have been corrupted?

Could have crashed, you carried on using it and it overwrites/corrupts it.

 

Try a reset and if it doesnt come back it'll have been wiped

How would do a reset? Wouldn't that wipe everything though?

Simply reboot the device.