"Your mother lost her letter."
Translation:Chaill do mháthair a litir.
How to know if a refers to a masculine entity in this case, where lenition is not possible?
If one could not discern it based on context, how woyld one ask for clarificatio?
Well, some dialects actually have a lenited <l>, so you could tell from there.
But, really, you'd probably just ask "Whose letter"? to clarify it.