We need a bit more information such as:
1) Are you performing the find manually? If not, what is your script and if not, does it work if you perform the find manually?
2) What is the data type of the field you are searching and what is the data inside?
3) Are you sure that data exists? Can you find the record and copy the data inside and try searching that way?
4) Are you searching the current table or do you have a related table involved?