[Freeswitch-users] Transfer back to origin on failure

When I do a blind transfer then I want freeswitch to call back the origin who initiated the call. But I am not able the capture the transfer event? <condition field="destination_number" expression="^att_xfer$"> <condition field="destination_number" expression="^is_transfer$"> They seem do be ignored by the dialplan. Is there a list what kind of values destionation_number can have besides the called numbers? I am doing the transfer with a grandstream gxp2140