Origin and usage of あせた


I often hear "あせた" as in:

> パスワードわかんなくてあせた  
>  作れなくてあせたわ  
>  久々すぎて全然できなくてあせた

Is it only oral usage?  
How should I write it in an email?  
Does it make sense to ever spell it with kanji?  
I always hear it as "あせた", can it be used in other tenses as well?




Apparently the correct term and kanji is 焦った (to lose one's mind).

Thanks to ssb for the tip!

