as u said ur daughter is ill with high fever
..sometimes when we r lean or thin and veins are deep its difficult to draw the blood as the veins are not identified properly..
and even in weakness the veins get punctured easily wasting the vein we get..
anyways improper technique may be one of the reasons too.. but usually when we dont get blood from the veins we just move the needle abit to get into the vein so thats a normal process..
anyways u need not b anxious enough as the doctor ther will take care of all this if u just speak to him..
if fever reduces then no need to worry or else again go for blood tests..
take care and speak to ur doctor and he will solve but nothing to complain..