Hey Joe,
I am not sure I entirely follow what you are trying to accomplish, but if I understand correctly, you want to pass in two parameters and, if one is empty, use the other one. Assuming this is accurate, you could create a variable at the beginning of the microflow, lets call it RequestID and, in setting the value of that variable, have an if statement like this:
if $RequestName = empty
then
$RequestWF/RequestID
else
$RequestName/RequestID
Then you can use that variable to retrieve the object you want and continue with your microflow. No need for if then branching in the microflow itself.
Hope that helps,
Mike