Doc
I believe that the yaw was more due to the transient effects of an engine surge than a permanent large loss of fan flow capacity.
In the events where a single birds messes up the fan, as long as there is not a large rub-out of the fan rub-strip at the fan blade tips and the airfoil of most blades are still present to pump air, the engine will recover at a slightly higher N1.
In the events where the remants of a fan blade failure take out the fan tips rub strip over a large arc than the engine will either run down (older engines) or on new models, recover at a lower power by opening up bleeds.In the later case the actual thrust produced is unreliable at the gages and even may result in loss of N1 signal as well as EPR, although the EEC will synthesize a fake N1 in order to maintain what it thinks is being commanded by the throttle setting.