Current return path when using an AC coupled transimpedance amplifier
Every op amp has a differential amplifier at his input. 



And every transistor needs a "base" current to flow to work as the amplifier.



And this is why any op amp needs the DC path for his bias current (the inputs cannot be left floating). 

In your example, the non-inverting input is connected to GND. 

And the return path for inverting input current is "closed inside" the opamp.

The current will flow from the opamp input via feedback resistor into the opamp output node and to the GND via op amp output transistor. 

This diagram tries to show the situation