The last keyframe is still there (usually) If you go into the spline editor and select 'fit' you will probably find the keyframe you're looking for.
If not (perhaps because of a different global in/out) you can always first copy/paste the transform tool in your original comp, go to the last frame (your intended first frame) remove the animation of your copy (which will result in an unanimated transform that's in the right position) and copy/paste *that* transform and animate from there.