Has my lifter failed?

I am putting my 429 back together after replacing the pushrod's after one failed. While tightening the roller rockers to spec all of them have given me solid resistance but one. I pulled the lifter back out and with a little effort using an old pushrod, I can easily push the lifter plunger in and out.

Has that lifter failed?

Can I rebuild a bad lifter or am I in the market for a new one?

Thanks again for all your help....

Did you prime the engine and get oil coming thru them be for trying to adjust them if not it could have leaked down most of the time when you pull the push rods the lifters will bleed off and need priming to build them back up

probably just leaked down, Like's already been said.

The engine has 1000 miles on it and the lifters soaked in an oil bath over night. The lifter in question is in an oil bath right now and I keep pumping it to force any air out, no pressure as of yet...

They generaly will not pump up in a oil bath, by hand, if your so that sure its bad, get one lifter (or sometimes you need to buy them in a pair).