Searching for someone who went missing while riding helium balloons, ???? Here's some of the problems and some questions that would need to be answered before anyone can even begin searching. Weather conditions: Heat, humidity. Was it a hot humid day, early morning, or later in the daytime? It matters because the balloons would not rise as far on a hot and humid day. Wind conditions: Both surface winds and winds aloft at various altitudes. Again if it was a hot and humid day the balloons would not rise as far. And thus the surface winds would be a factor. But if it was a cool morning breeze, then the balloons would rise to possibly a very high altitude. In that case the winds at altitude could have blown the craft nearly anywhere.
How far inland is the site where he departed? Was it close to the coast? Which coast line? Brazil is a big country. If it was on the western coastline, and if the winds were blowing easterly, there are plenty of very high mountains and forest to search. And not very much new imagery if any.
It is not that we here are not sympathetic to the problem of a missing person, much less a priest. There are many problems that need to be solved before anyone can even begin to search for him. I suggest you try to contact one of the satellite imagery companies to see what can be done in terms of obtaining new images. But you will have to know first where to begin. That means knowing something about the weather conditions on that day.