Hi Veg,
Your friend must have had mono (a virus) combined with a bacterial infection such as strep to be on antibiotics, since mono isn't a bacterial infection. If your friend was still in the really active stages of mono/strep (ie: really sore, infected throat, fever) it is conceivable that you could catch it - since they are both spread through saliva. However, the liklihood is low that you will get it. If you have already had it the chances are almost nil. Hope this helps, j.