Need help with a circuit diagram where the motor does not seem to have any connection to ground. Error with diagram? Or am i missing something?
The shockingly badly drawn circuit diagram (from the cited article) is wrong.
There should be a connection from the Q1 transistor emitter to ground (ATtiny pin4, battery negative).  The transistor will then be driven on in the usual manner by R2 = 3.3 K Ohm.

As drawn diode D1 has minimal effect and R3 is of no real value.
Better would be to connect D1 across the motor (Cathode to B+) so that the diode does NOT conduct when the motor is being driven and acts as a "freewheel" diode when the transistor is off. 

The value of R2 (= 3k3) will provide less than 1 mA drive to the transistor base and depending on the transistor used may limit motor current. A value of 1K Ohm or even lower may produce better results.