Hi Sheila,
Yes, you should pretend it never happened and just be yourself the next time that you are around him at work.
You don’t have to pretend to be happy if that isn’t who you are. Just act naturally.
At the end of the day, he may not have felt like he ghosted you. He never made any promises that the both of you would meet. You were the one who sent him that text about meeting up.
He never made any promises to you about the possibility of meeting up nor did he arrange an actual meetup with you.
Again, technically, he may not feel like he ghosted you. You may feel that way because you have feelings for him and were affected by the fact that you never got to meet up with him that day.
However, it is important to try to look at the situation from his perspective.
With this understanding, it would be best not to call him out on ghosting when you see him again at work.