Sorry for my scepticism in the post before - it sounds more reasonable with your further explanations. I hope you can keep the diseases on a low level. I know thats possible with fishes, but (luckily) dont have experiences with Mycobacterioses in Amphibians.

I have seen the vendors displays in Hamm, this should be no problem for a healthy animal, if its for one or two days. More problematic are suboptimal conditions and stress over long time periods. It is always a risk to buy Amphibians at expos or in the pet trade as you never know how the animal were kept before. Best is to go to a breeder directly.

Wish you good luck!