I'm so sorry for your loss...
Just a few things:
1. Frogs do not get lonely, I believe this has been proven scientifically.
Some frogs are social, meaning they do well in groups. Like darts. But Trevor is definitely NOT lonely, nor does he miss Kevin.
2. As mentioned by many members in your other post, NEVER mix species of frogs!!! It is soooo important to always follow that rule. Not only do darts and your Baja California Tree frog require different environment needs, they could poison one another. All frogs secrete toxins that are not compatible with other species of frogs....
So, if you want some darts, do your research, get a different enclosure, set it up, and then get your darts.
I have to say, I've had my eye on darts for a while also, they are sooo cool
Good luck