That is yet another fact about Johto there's really no need to boggle yourself over. Some people return with memories, some don't. It's really hit or miss. Usually miss. And how exciting. Where are you headed? I could possibly give you directions that might make it a little quicker, and even assist you should you be too far out by the time the party is happening.

[[Mamma Rose is totally willing to loan you Pokemon/come pick you up with Fly if need be.]]