Leaving out one fatty acid does not make it a trans fatty acid.
A trans fatty acid is the geometry of a unsaturated portion of a fatty acid or the angle of the double bond and the single bond on each side. For brevity I only show a small segment of a fatty acid

.....C-C=C-C.....
(C) is a carbon atom, ( = )is a double bond or unsaturated site ,
( - ) is a single bond

The natural geometry is in a U shape or CIS position,in other words the first carbon atom (C) is angled up and the last carbon atom is angled up. In unprocessed(no high temperature exposure or partial hydrogenation) fatty acids with a double bond is in the CIS configuration and occurs 100% of the time.

In a Trans fatty acid the first carbon atom( C ) shown is angled up and the last carbon atom is angled down . This results in a shape of a lazy s or ~ (tilde) called Trans configuration. Trans fatty acids are the result of heating the oil to a high temperature or hydrogenating the oil. Hydrogenation eliminates some or all of the double bonds ( unsaturated sites)
The FDA will soon require labeling of the amount of trans fatty acids in foods. These Trans fatty acids are suspect in cardiovascular disease as well as other heath issues . To my undersatanding , trans fatty acids get into your system and become incorporated in cells .The problem is that the geometry
of trans fatty acids is incorrect to properly function in metbolic systems. There are some good sites out there about trans fatty acids.
Man .... can i get long winded.