Used clindamycin cream and then azithromycin for gardnerella. vaginal swab test of cure showed no gardnerella and also no lactobacillus now. possible sample error? or is it expected that lactobacillus would have been completely eliminated too?

Yes, these drugs could well have eliminated lactobacillus. This is one reason that these drugs are not the first choice for bacterial vaginosis (which probably is what you mean by "gardnerella"). The treatment of choice is metronidazole, which does not inhibit lactobacillus. (Gardnerella itself is not abnormal. It is just one of many bacteria that overgrows in women with BV.)