The awhile/a while grammar error is, obviously, more of a written error than a spoken one. Awhile (one word) means for a period of time, as in Grandpa waited awhile before turning himself into a bat. It already includes the word for in its meaning.
A while (two words) means a period of time, as in Grandpa waited for a while before turning himself into a bat. Here, you need to add for because it is not included in its meaning. Please don’t use the word for when using the word awhile, as in Grandpa waited for awhile before turning himself into a bat; that means Grandpa waited for for (no, you’re not seeing double) a period of time before turning himself into a bat.
Sherry
Sherry’s Grammar List and Paul’s book–Literally, the Best Language Book Ever
Everything Language and Grammar 