Unfortunately there is not a pre-existing, direct method to do this from the Lotus Connector for SAP.
You would not be able to use Virtual Attachments, because the SAP Connector specifically does not support it:
http://publib-b.boulder.ibm.com/lotus/c2735021.nsf/b3266a3c17f9bb7085256b870069c0a9/bb7d63a3dd15246a652577910055117b?OpenDocument
There is also no binary data type that we can grab from SAP:
http://publib-b.boulder.ibm.com/lotus/c2735021.nsf/b3266a3c17f9bb7085256b870069c0a9/3775b2ee0e4621f0652577910055ee42?OpenDocument
There are two choices to transfer attachments:
1. Detach the file to your OS, then use LotusScript to access the file
2. Write a remote-enabled BAPI that contains an argument for where to place the attachment, then call that BAPI from LotusScript.