Hi there. I'm not quite sure what your questions are, but here goes. First off, let me say that the term "juvenile" diabetes is no longer used. There is type 1 (T1) and type 2 (T2) among a few others.
It is quite possible to get T1 at any age. Were you told you have type 1? As I said, it's quite possible.
As a long term T1, I can say that it is also possible for what happened to you. My suspicion is that part of the food you were eating was being covered by the lantus. That can happen when you take too much and consequently, you end up taking a bit less of a bolus than you would otherwise need. Would you would find you went low previously when you didn't eat? That would be a clue.
Anyway, I hope I helped a bit.