in field fly or not

Question
recently had a runner on 3rd and a line drive was hit to 3rd base as well ; the runner left the bag at first contact of bat. the 3rd base caught it and ran and tagged his base and they called the runner out.now the funny part is it was my team defending and i immediately said she is not out as the 3rd baseman did not tag her . in which i replied she is safe. am i in the wrong! does it revert to a forced play to her to get back to the bag?  signed really confused. they started calling on an infield fly rule! i replied it did not go above backstop therefore is not an infield fly not to mention there was no runners on 2nd or first. please would appreciate clarification on this.

Answer
hi jacked,

this would not be an IF because 1st and 2nd weren't occupied.  Also the height of the backstop has nothing to do w/ an IF or not.  An IF cannot be a line drive or a bunt attempt, that's it.  Anything else in the air can be an IF.

Ok line drive caught by F5 who then steps on 3rd ahead of the runner off base.  The runner is out but this is not a force play.  It is a live ball appeal of a base left too early.

Mark