First I'm sorry you had such a bad experience but it sounds like nurses who thought you were exaggerating your discomfort.
At least your doctor was on the ball when he saw you.
Spotting is very very common post hyst.
unless you have your cervix and ovaries removed that is.
ovaries are typically left in place unless you are at a high risk of ovarian cancer, as they continue to produce hormones that can decrease your risks of conditions such as osteoporosis.
if your cervix is left in place then they also leave a tiny pocket of uterus.
this tiny blind pocket can and often does contain a small amount of endometrial tissue - which can also be found in the cervix sometimes as well.
this tissue responds to the hormones produced by the ovaries and so you do get cyclical spotting.
However this should never be taken for granted.
other causes of spotting can include a small patch of tissue that didn't fully heal and can be treated with a simple silver nitrate treatment.
You should definately, in light of your experience, get this checked out, but I do (and I am not a medical professional) expect that it will be one of the two situations outlined above.