It has been my experience that a noun coined by truncation looses its apostrophe pretty soon after it is coined. I should think the reason is to avoid conflict with the possessive. On the other hand, words like goin' (shortened going) tend to keep their apostrophes. In Texas, nobody puts the g on the end of a verb so it may as well be left off in writing. I know, the world is not comprised of Texas. There is also Australia!!! Philip Hudson