"I Hope that I didn't cause any confusion; however, what you stated is new to me, as I have not ever heard of a dog going into heat for the very first time at 17 months plus. I'm not saying that it's not possible, I've just never experienced it, not even with the much larger breeds that I've had in the past. I worked as a vet assistant for some time and have not witnessed this there either. Though, I have heard of dogs coming into estrus much later than 12 months, 17 plus months is shocking to me. I know that many times a heat can go unnoticed. This si what we'd call an invisible heat. The owners may not be aware of a heat cycle or how to recognize all of the signs. They may have just missed it, but wow 17 plus months, that's new to me. Thank you for sharing your experiences."
Yeah, it happens. And as I travel I see it more. I just whelped a litter of GSD's that the bitch had her first heat cycle at exactly 18 months and the vet's couldn't determine anything wrong w/ her to cause it. All other progeny within two generations came in on average at 11 months. Interesting, huh? If you ask your vet, pick up a well known/read book that is used for reference by veterinarians it'll have something to the like in it.
Oh, and I'm w/ you on the vet tech. tip! I went to college for a Zoology degree!
And I'm quite aware of the signs/symptoms of a heat cycle, even ones where the bitch really doesn't bleed much if at all.
Just saying it's not common, but it does happen.