It would depend upon when the amendment was filed.

If the amendment was recorded after the recording of the new deed, then I do not think the IRS has a strong case for attaching to the property. It may have to go to court, but I cannot see a judge allowing a bona fide purchaser to be punished for something that appeared to have been cleared - and was not of record - at the time of the sale. It seems this should follow the same rules as if the IRS did not refile the lien within the 10 year and 30 days period provided by law.

If the amendment was filed prior to the recording of the mortgage, then the IRS has a stronger stand and this becomes a claim under the Owner's policy that was (hopefully) issued.