Like the 10000 other things they tried.
1. Did they plant it themselves during the raid
2. How did he get more documents to begin with?
3. No one, not even lawyers were allowed to observe during the raid so anything left was left by the FIB t begin with.
4. And cannot be repeated enough, Trump was the sole keeper of classifications, as president he and he alone had and exercised authority to declassify everything.