That's probably just bad game design that you've run into. Done well, an "unlock" ability should either grant access to more space off a central hub (that you'

That's probably just bad game design that you've run into. Done well, an "unlock" ability should either grant access to more space off a central hub (that you'd be returning to anyways) or give optional minor rewards if you want to be the completionist back-tracker - zelda pieces of heart, or max mana upgrades; metroid missile capacity; even raw cash. Being forced to backtrack (especially without fast travel) to an arbitrary area _to progress the game_ is bad design.