The instructions for the SFHDF state:
3. LENDER ID NO: The lender funding the loan should identify itself as follows: FDIC-insured lenders should indicate their FDIC Insurance Certificate Number; Federally-insured credit unions should indicate their charter/insurance number; Farm Credit institutions should indicate their UNINUM number. Other lenders who fund loans sold to or securitized by FNMA or FHLMC should enter FNMA or FHLMC seller/service number.
Also keep in mind if the loan is sold you must notify FEMA: https://www.ecfr.gov/cgi-bin/text-idx?SID=0508ca16a4bebb26037f5ad014cb8521&node=12:5.0.1.2.28.0.3.10&rgn=div8. Check with your flood vendor to see if this is something they do and what you need to do, if anything.