Balloons with messages that were released (here) have been found in Europe. They go up until they a.) catch the jetstream, and off they go. b.)until they go high enough to pop, but still the rubber can travel a long way before it returns to earth.
I have sent up many, but never got any replies.
Once when they were having some special ceramony at the old Cleveland stadium, they release a giant bunch of ballons. Later in the day my kids started yelling for me to come outside. I went out and the whole flying field/orchard/backyard were filled with helium ballons! (I live 35 miles SE of there) These balloons went up, got wet, then came down all around my and nearby properties. We took a couple hundred into the house, and dried them off, wrote messages on them, and re-released them. Never heard a word from anyone who may have found them.

Jetts