The one month of comp, I usually do not have a period. But by then, I was so physically and mentally drained of everything and I was pushing myself way beyond my limits. There was no way this female body could make a baby at that time, so it gave up. But as you ease up, the body decides that it is OK to make a baby and the period begins again right afterward you ease up. Intensity always pushing forward will make your body decide not to produce the hormones as it is not a good time to procreate. As soon as you ease up a little, you give the body the idea that you will continue to ease up and it makes the hormones needed.
I think if you just ease up alittle on your training, say do a low intensity cardio instead of high intensity all the time, and maybe gain only 1% bodyfat back, you will get your period. If not, then I would be concerned that it could be alot of other things that could go wrong that I would personally get it checked out (endometriosis runs in my family, so I have to be on guard for that). Just having a vegan diet is not a good excuse for not getting a period. All women athletes who push themselves pass the safety zone, can lose their period. But like all good athletes, it is just for the one time event - then they ease up and go back to the safety zone for health reasons as you stated to having your period (circulating hormones in the blood stream do more than just begin the menstrual cycle).
Your guess would be wrong on the vegan female athletes being less than 20% bodyfat due to their diet. My body type is a mesomorph, with an incline towards endomorph without exercising - so I am pretty big - even on the raw vegan diet! My metabolism is very efficiently at getting every calories out of my food. LOL!