It's been a while since i did some phospholipid stuff, but as I recall, after doing some LC-MS on a lyso-PC standard, I came up with the same sort of peak in front of the peak.

If you do some MS on it, you can probably confirm the molecular weight and see if it's something else. Avanti polar Lipids has some good info on Phospholipids.

Also, and I'm going on straight memory here, using ELSD or cCAD don't you pick up certain chain lengths? I remember looking at a reference standard for Phosphotidylcholine and seeing 2 peaks. Based on MS we concluded that we had 16:18, and 18:0 PC.