Apparently i was never given the grappling hook...
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It's possible to get upgrades for the grappling hook before unlocking it, though if you do pick up an upgrade, when you get the grappling hook the upgrades will already be in effect.
On the Testing chambers level, the grappling hook can be found at the top of the blue tower once you reach the big dome area.
On the Desert mine map, the grappling hook can be found about halfway up As seen here (timestamp is 10:55)