I have a new client who took a $20,000 premature distribution from a 401(k) plan, but did not self-assess the IRC 72(t) penalty on her return. She used the monies to purchase a first home.

I am aware of an exception to this penalty if the premature distribution is from an IRA (up to $10,000). Had she rolled over a distribution to an IRA, then distributed the $20,000, half of the distribution would have been exempt from this penalty.

Are you aware of any PLR's or other cases in which the taxpayer got out of the penalty for first time home purchase from a 401(k) plan?

No exceptions that I'm aware of. Your client almost certainly owes the penalty tax.