Pokemon Heart Gold Soul Silver – Can Pokemon Caught on Pokéwalker Have Hidden Abilities

In HeartGold/SoulSilver if you faint any legendary, they will "respawn" each time you beat the Elite Four. They should be at the same location (if they were not roaming), except Suicune who goes back to the Burnt Tower according to this.

But if you want to make sure you catch them you can save your game regularly then reset when you come across them. You'll also do well with any of these:

• Using a Quick Ball on the first turn, or other appropriate balls like Dusk Ball at night.
• Paralyzing them
• Using False Swipe
• Using a fast pokemon that knows Mean Look (e.g. Golbat/Crobat).
• Use a pokemon with Arena Trap or Shadow Tag (e.g. Wobbuffet)

There are at least three ways. Unfortunately, none will work on your scenario.

Fling, when used with a corresponding status healing berry, should recover the status condition. However, it counts as a 10 Power attack prior to causing the effect, so you would not even be able to throw a Sitrus berry for healing before you would kill something at 1 HP.

Trick and all of its derivatives can be used to swap a status healing berry onto the target. None of the Legendary Beasts have held items to my knowledge, though, so this won't work.

Finally, the moves Wake-Up Slap and Smelling Salts will cure Sleep and Paralysis respectively. But not only do they do damage, they do double damage to such an afflicted Pokémon. So like Fling, not viable.