Small Engines (Lawn Mowers, etc.): repairs to a Honda Harmony lawnmower, oil leak, oil level

Question
We gave our Honda Harmony to the local dealer for annual maintenance.  They did the standard stuff plus changed the blade belt.  Now the mower has an substantial oil leak, which it did not have when the mower was picked up.  Brief conversations with owner have been fruitless and he contends that nothing they did involved the engine.
Any guesses as to what could have happened to the mower while in the shop to cause this sudden and unexplainable oil leak?  BTW, the oil leak appears to be major.

Answer
Daphne,

I would monitor the oil level on the dipstick of the engine.  I suspect what prob happened is some oil spilled out when they drained it.  Keep a close eye on the oil level on the dipstick.  

Its hard to cause an oil leak while simply doing a tune up