If things went down exactly as you described I can't see how anyone could be justified in complaining about you; you said you were polite and gave exactly the same level of care as for any other patient, but just weren't "warm and fuzzy" with it. It's easy for someone who wasn't there to say, but do try not to let it worry you. If I may add a personal note, I've recently started my Tech training course (not with LAS) and we were told in our first week that 95% of complaints are about "manner and attitude". Once I'm turned loose on real people, apart from cocking-up completely (which I hope my mentor won't allow me to do) this is the thing that worries me the most, especially since I've never been one to suffer fools gladly.