I"Ve had a LOT of dogs and I would not know to look in the inner rear leg for ID. In fact I have never heard of tattooing there. I'd check the collar first, then the chip.
People naturally look inside the ears of dogs they find for ticks.
I cant imagine that there is anyone on here that doesnt check their dogs ears on a normal basis. We uust dont think of it.
I have chipped two dogs and lost both ( at the same time). Called the chip hotline and wa as told only about 15 -20% of chipped dogs are recovered. Vets do not check to see if a dog iss chipped unless asked too.