If there's a grinding problem in the mags it could start.
I reckon you mean a _grounding_ problem? But it is extremely unlikely. If you could stop the engine after your last flight by short-circuiting both circuits (and Rod1 is right, there are no magnetos properly speaking) then the grounding circuit is all right. And even if there is a fault, it is very hard to start a 912 by hand propping, due to the gearbox working against it.
You want to ressaure yourself? Try handpropping your Rotax - you'll have a hard time, and small chance of success. Especially if it is cold.
Last, but not least: gurgling is indeed standard practice for 912'ers, can be found in all engine/airframe handbooks. Whoever told you not to do it (by which I mean: specifically on a Rotax 4-stroker) is, err, less than sufficiently familiar with this type of engine (to put it as politely as I could).