I have heard about silent heats - I am sure that if you do an online search you would be able to come up with something. It's not that uncommon, especially in the smaller breeds. She is still young so you will more than likely notice her being in heat when she comes in season next time. Nothing to worry about though.
__________________  Tracy and my  S 
" If a dog will not come to you after having looked you in the face, you should go home and examine your conscience."- Woodrow Wilson |