It depends on how the data is saved. Is it in a UDT with records saved to a random file using PUT #?
[tt]
TYPE MyRecord
LastName AS STRING * 64
FirstName AS STRING * 64
IOU AS DOUBLE
END TYPE
[tt]
Or perhaps saved sequentially to a file opened for output or append using WRITE # or PRINT #.
In either case, you need to loop through the records until you find the name or a combination of last and first names.
If you are simply looking for the first occurance of a string (say "Bob Smith"

in a file, you can read the file into a larger string and search with INSTR.
[tt]
ff = FREEFILE
OPEN "MYFILE.QAZ" FOR BINARY AS #ff
GE$ = STRING$(LOF(ff), 32)
GET #ff, 1, GE$
CLOSE #ff
BobIs = INSTR(GE$, "Bob Smith"

IF BobIs > 0 then
PRINT "Found Bob Smith at file position" ; BobIs
ELSE
PRINT "Can't find Bob Smith"
END IF
[tt]
Naturally, if the file is larger than 32767 bytes long, you will have to find a smarter approach.
All of this depends on how the data is saved and what you are trying to accomplish.