I also ghosted my dentist during Invisalign. In my case, I was just an non-compliant teen before Teen Invigalisn (which measures compliancy according to hours worn) and I just couldn't keep up.

The first 6 months, I showed up and did as instructed, but eventually gave them the slow fade (missed appointments, cancelled etc.) I stopped using the trays at all after a while(I ran into a bump in the road, they stopped fitting properly, and I probably needed a readjustment).

Once I grew up a little, almost two years later (during which I actually thought about my teeth often and worried), I called the office.

My denist, at the time was an absolute angel, and agreed to continue treatment, which I completed successfully the second time.

He hadn't cancelled me and he had access to everything. I needed and received a readjustment (I think three were included in my plan). That's all. Almost like nothing had changed.

I'm sure this kind of thing happens often. So, just ask :)

...Also, definitely pick the permanent retainers if possible. Chose the non-removal, adhesive, and, stuck version of dental things going forward.