With a little bit of investigation on your part, you may be able to find this information yourself. In many states (at the county level), the foreclosure listings are public record.
What county was your father's property located in? May I assume it is in Queens County? Contact the county assessor to find out how foreclosure proceedings are handled in that county, or call the Residential Foreclosure Office of Queens County at (718) 298-1092 to ask for their advice.
Any foreclosure will legally be handled by a court case and your father and his heirs/family should have been notified by mail when the foreclosure was taking place, although your father may not have been notified if whoever was handling the foreclosure did not know his mailing address at the time.
Do a search on the following New York court case website, using your father's first name and surname as search terms, to see if any relevant foreclosure cases come up with his name:
https://iapps.courts.state.ny.us/webcivil/ecourtsMain
I believe you will find the relevant foreclosure case and you can then visit the courthouse to look at the file to see how the case was handled or order documents from the case by mail.
If you know any attorneys or paralegals or any members of the general public who have access to the PACER federal government database, you could ask that person to do a search, using your father's name as a search term, to see if the foreclosure case is listed there. There is a small fee required for that search.
Do NOT sign a contract/fee agreement with any asset recovery firm unless you can not find the information from other sources, and even then, you should negotiate by suggesting, for example, that they reduce their fee to 10% instead of whatever they are asking for (many such services ask for one third).