The committee believes it has been sent by Malcolm McKibben to the permanent secretaries of government departments.
Committee chairman Daithi McKay of Sinn Féin said: "I am keen to see that very soon because I am aware there are some efforts to stymie this inquiry."
No witnesses appeared at the hearing.
Most of the session on Thursday was held in private.
The committee took stock of correspondence it has been sent, including from loyalist Jamie Bryson, who claims to have information about the loan sale.
Sinn Féin MLA Michaela Boyle said: "Reading Mr Bryson's letter he is a person of interest and we did put out the call for anyone who may have factual information to bring that forward.
"We are not in the business of shutting doors on anybody. Factual information should be brought forward."
The committee agreed to write back to him, asking for any evidence "within its terms of reference".
The Law Society is due to appear next Thursday.
The Nama Northern Ireland loan portfolio was sold to the US investment fund Cerberus for more than £1bn last year.
Irish politician Mick Wallace has alleged that £7m was due to be paid to a Northern Ireland politician in the wake of the deal.
Mr Wallace told the Irish parliament the money had been moved for that purpose to an Isle of Man bank account controlled by the Belfast solicitor Ian Coulter.
Mr Coulter is the former managing partner of Tughans solicitors in Belfast and worked on behalf of the buyers in the Nama deal.
He said he had directed that money be transferred to the Isle of Man account for "a complex, commercially and legally-sensitive" reason.
He said no politician, nor any relative of any politician, was ever to receive any money.
BBC Northern Ireland's Spotlight programme has established the Isle of Man account was intended to facilitate payments to non-lawyers or deal fixers.
Stormont's finance committee has said it wants to see a letter the head of the civil service has written regarding the National Crime Agency's investigation into the NAMA loan sale.