A follicle once ruptured cannot rupture again. In case of follicular stimulation through hormones, more than one follicle may develop and rupture at different time periods. If you had a ruptured follicle on day 10, it would have shown on the sonogram; it was not so and moreover, the follicles grew in size. Taking a test for LH surge or basal body temperature
measurement are the other means of knowing the occurrence of ovulation. Right now, the only way left is to wait for your next cycle and go for a pregnancy
test if you miss it. Take care.