🚀 go-pugleaf

I just finished an Electric Circuits Lab and one of the circuits
involved an op-amp where the op-amp had its two bipolar power supply
connections, and a signal generator was feeding a sine wave into the
non-inverting input of the op-amp.  Then, a direct connection was made
from the output to the inverting input and the gain was measured.  It
was found that there was no change in the gain.  Then, the same
circuit was used but instead of the piece of wire going from the
output to the inverting input a 27k resistor was used and the gain
remained the same although one would have thought it would
decrease.(At least I did anyway!)  Is this because there was no second
resistor that would normally have gone from the inverting input to
ground?  That is all I can come up with because the formula to
calculate gain is Afb=(Rf)/(R1) + 1 for closed loop gain.
Can anyone verify that my assumption is correct or not?
                                  Thanks, Rob