Four weeks ago I had my oil changed (106,000 miles), and today I noticed some oil on the floor. I don't know if there is a problem or whether something was not done correctly when the oil change was done. The tech is a Lexus certified tech who does work for a Lexus dealer, so I am sure he would have noticed a leak when he changed it. I looked underneath, and even though I only had a little on the floor....three drops size of a quarter, underneath the engine area looks fairly wet.
Thoughts please

Your drain bolt is not on all the way, the rubber seal from the old oil filter never came off and is still on there with the new one, oil filter is not tightened all the way, your oil pan is leaking. Some things that may be it

Go back to service and tell the tech what happened if you see more oil drops.

Oil drops found on the floor after an oil change does not automatically indicate oil leak. In the process of removing the oil filter, there is a good chance that some old oil spilled onto the nearby parts or the engine under-cover. The residual old oil will make its way onto the floor eventually. I agree with Htony - take the car back and let the tech deal with it.