How about a little information here?
Male of female?
Did you take before pictures?
Have you taken progress pictures?
Do you clear the entire area each and every time you have treatment?
Have your appointments gradually become shorter and shorter (unless you keep adding new areas to work on as you finish the main area sooner)
The one thing I can tell you for sure based on what you have stated is that your hair cycles would have only just gotten close to having shown every hair one time over the period you have been working on clearing this area. Although the quickest one could possibly get done would be 9 months, most people require 18 to 24 months to finish based on many variable factors.
Yes, during that time you will likely go from totally cleared, to the next phase of untreated hairs coming in, and presenting themselves for possible treatment, if you get them worked on before they start to go into shedding phase. Since one doesn't notice a difference in hair growth until at least 50% of the hair is removed, it is easy to understand why you might think that "it all came back", but you should know that you have experienced a reduction. Progress pictures would show this if one kept at taking them over the treatment process.