Your question is a good one, but it is slightly misguided. You are seeking a precise definition for a term which does not have one. The word Protestant can mean different things depending on the context in which it is used. When used in a historical context, it may be used to strictly refer to those involved in the Reformation and to the churches that they directly founded. However, it is also perfectly legitimate and acceptable to use the term Protestant to refer to any Christians or Churches that espouse the same principles as the original Protestant reformers.
The biggest commonality among Protestants is that they denounce the universal authority of the Papacy. Beyond that, the term Protestant is much like the term Christian. It essentially applies to anyone who chooses to apply it to themselves. In that sense, I do think that you were using the term appropriately, as long as you only intended it in a loose way. It would be wrong to correct someone's use of the term by suggesting that the term can only legitimately be used in a historically precise way.