Engine oil sucked into valves!

A few weeks ago while driving normally, the "Check Engine" warning flashed on the TFT display panel. At first, I thought its O2 sensor went kaput which is a common issue from what I've read.

Since it was also due for annual service, F-SB generously offered to pick it up with their flat bed tow truck without added cost. The unwanted surprise came two days later when the Service Manager informed me that engine oil had been sucked into the valves and it'd cost over $3k just to clean the mess up!

Now being a Mechanical Engineer by profession experienced in the design of hydraulic / fluid conveyance products for Commercial and Military Aerospace and Space applications including years of supplying innovative valved products for Ferrari F1, I was also quite familiar with dry sump engines and a huge no-no is to overfill when replacing or topping off engine oil.

However, I hadn't even opened my car's hood given that it sat mostly last year when there were pandemic travel restrictions since it got its last annual service in January 2020. So I was rather disturbed, ticked off and baffled how such a major problem could've have occurred! Besides, the only time it was at another facility for several days was when F-LA towed the car when its battery died due to non use (I've since started attaching the battery conditioner).

Regardless, it was only my word and assurances I hadn't even touched the engine as my reasoning (that plus $2 will not even buy anyone a cup of Starbucks) so I had to grudgingly agree to fork over $$$!

Has anyone ever experienced such a phenomenon happen to their 599 or similar engine? What could have been the problem's root cause? I appreciate your expert opinions. Thanks.