It's unlikely to cause any long term damage. You don't say how much coolant it took when you topped it up, if the header tank was just on the minimum then we're not talking much really. If it was well down, say two or three litres, then that's another matter as the system normally only holds about five litres.
You could still have a leak even if it's not showing anything dripping to the floor. If the cylinder head gasket has gone, the coolant can be boiling away, or getting into the oilways (check the engine
level hasn't gone up). These are just general pointers, not specific to a Laguna, there may be other places the
and cooling systems meet apart from the cylinder head (my Laguna is still new to me too), and
cooler for example.
If you have access to a cooling system pressure tester this can be used to pressurise the system to pinpoint any leaks, or ask a local garage to test it for you.