Well... from my perspective time does heal a lot of wounds (not all of them.) I can't say I've been through something like this exactly. But, over the years (decades really) I just become permanently sad. I wouldn't go so far as to say I never smile. But I don't smile much. And when I do smile, it typically tends to be more of a smirk than a genuine smile.

Yes, your smile may well come back given time. However, since you mention you've done meditation & yoga, here are a couple of thoughts. I've read that there is research showing that smiling, even if it's a forced smile, tends to brighten a person's perspective over time. Apparently there's something about using the muscles that create a smile that elevates a person's mood. And in line with this, forming your mouth into what is typically described as a "half-smile" during meditation, is something one often sees recommended in books on meditation practice.

The other thing I would mention is that, from the perspective of the ancient Tibetan Lojong ("mind training") practices, something such as you describe would be considered an excellent opportunity for practicing mindfulness & self-compassion. It is a practice referred to as compassionate abiding. Here's a link to a mental-health-oriented description of the practice:

https://mindsetdoc.wordpress.com/201...e-abiding-101/

May it be of benefit.