Honda Civic Hybrid 2005 suddenly stopped running

I was told by Honda tech that the lost motion assembly came loose and had lodged into the camshaft. The camshaft stopped and then broke the camshaft gear pin that holds it in place. The camshaft pulley then spun freely and the motion of the car engine bent the values. Does the tech explanation pass the giggle test or as they originally told me they don’t know how it happen?

The “lost motion assembly” must be strictly a hybrid term, because I’ve never heard of it in the past. Providing it is a hydrid-unique part, and not really referring to the cam sensor or timing belt or something else, I have absolutely no clue on whether or not their explanation passes the giggle test or not. If I were you, I’d jump onto Google and start searching Honda forums and see if you can find someone else that had a similar problem as yours. Sorry I wasn’t of more help.

If the “lost motion assembly” is a part of the VTEC variable valve timing system…
then yes that explanation makes sense.
If some loose piece forces the cam to stop turning something has to give, like where the pulley attaches.
If the cam stops turning it’s just like the timing belt breaking.
This must be an ‘interference’ engine.

No, the Lost Motion Assembly is not unique to Honda hybrids. Any modern Honda engine with variable valve timing is likely to have these components.

As Circuitsmith states below, a malfunction in the Lost Motion mechanism can pretty much duplicate what happens when a timing belt breaks on an interference engine.

Did this engine run low on oil, or did it ever go a long time between oil changes?
Oil starvation often starts at the top of an engine.