Woodruff Key missing

[krwsenior]

What should have been a quick, simple change of the front seal on my 1991 350SDL has turned into a bigger problem. I can't find the woodruff key for the harmonic balancer. I'm afraid that it may have fell into the engine. Now what to do? Can I pull the oil pan without removing the engine or transmission? I'm sure it would be a bad idea to run the car not knowing if that woodruff key is in there somewhere.

This is my daily driver. I need it quickly. Any advice is appreciated.