No, but once a unit is rescued, it isn't recuable any more. The idea of rescuable units is that once someone recues the unit, they change to his team and aren't rescuable any more.
I see your problem. It may be a bug with the WE, but I would reccomend going into the Trigger Editor and at Map Initialization make the action Player - Make (whatever the rescuable player is) rescuable for All players.
Don't blame blizzard, they've done an amazing job as it is by making their great games. It's probably not that easy to fix those bugs also, considering that they're probably really busy with WoW, besides, not all of the bugs are just mistakes. Their could be some that are unfixable unless they want to totally changet the way the game works. You just have to accept the bugs and make the most of what you have.
Blizzard never knew we would take making maps so seriously - they mostly did balances and fixes with general melee games. Theres very little fixes and changes to the World Editor. I think people these days make more maps then playing the real point of Warcraft III - Melee games. Wc3sear takes map creation very serious because we get the best out of WE
I for one never liked "the real point" of warcraft iii (perhaps it's because i couldn't figure out it *g*) - i much prefer the maps which in Starcrafts day were called "use map settings"