Just wondering if someone can advise as to "how" this occured?

We just had an anonymous call to our VOIP account on 2Talk, however it only rang on our Softpone (registered using 0########-1), but our 'normal phone' via an ATA didnt ring at all (registered with 0########).The resulting voicemail message suggests "someone" was actually on the line, as you could hear office type noise in the background.

When a normal phone call comes in, the Softphone and the normal phone both ring, so Im wondering if someone has somehow managed to dial our "softphone connection" directly?

When I rang our line from my mobile, it all worked as it has for a few months ... both softphone and normal pone rang, and we get a call record in the 2Talk admin web interface. There is no call record for this anonymous call in the logs.