was gone の意味は？

this is not a piece of advice to you I'm talking to myself for my practice of writing skills.
GT'd not be good at reading between the lines/metaphor, also I'm too.
I'd introduce Kevin-san's saying that It's a good idea to try to guess what the person who used the word was thinking, from the situation at the time, and from the sentences before and after. Meanings are in people, not in words. I suppose it can be able to grasp any meaning depends on the situation.
I've tried to put your sentence into GT. GT's translation is the next sentence.
We arrived home to find that my cat was gone.
:GT.
https://translate.google.co.jp/?hl=ja&sl=en&tl=ja&op=translate
Kevin-san's saying
https://qa.weblio.jp/回答をしばらく休みます-82285