Nor, to the best of my knowledge, have I.
The question I was asked, though, was how I might respond if a Muslim person were to wish me "Happy Ramadan".
I think I captured the essence of how I would respond in my post.
What I most assuredly would NOT do is take offense simply because a person of another faith expressed to me a hope that I might be happy during the month of Ramadan (and I think I am correct when I say that there is, in the Islamic calendar, a month called "Ramadan", during which there is fasting and repentance. It is thus not exactly the same thing as Lent. As far as I know, there is no month of "Lent" in any commonly-used calendar.)
Not arguing with you, but it is quite unlikely that a Muslim would wish you, or anyone, a Happy Ramadan (because, as I said, it is a time of fast and penance.). Now, they might wish you a "Happy Eid," which are the days AFTER Ramadan when festing, eating, and parties prevail.
Ramadan is not the name of an Arabic or Muslim month. It moves, and is based on the Lunar Calendar. But because it lasts one lunar month, it is referred to as "the month of Ramadan." A few years ago Ramadan was in December-January. This year it was in October...having moved due to the lack of congruity between the lunar and solar/Gregorian calendar (that the modern world uses).
Lent, too is lunar based, although it lasts longer than a lunar month...it lasts 40 days.