not sure how you are using SUIM to check, just to be sure, use the complex selection method or the authorization values method. the by transaction method only check for transactions that were added via the menu.
look for object= S_TCODE, value=(the transaction code)
SUIM will then calculate if the transaction code was added manually and as part of a wild card or a range.
i.e. if the transaction was MM02 it will be accessible if the S_TCODE had
wild card value M*, MM*, MM0* or
range value A*-Z*
Otherwise, it is possible that it was called indirectly and the BADI does not perform a S_TCODE check.