YOU SAID:

I lost my wallet when we left grandma's house last night after we were done drinking.

INTO JAPANESE

昨夜、お酒を飲み終えておばあちゃんの家を出るときに財布をなくしました。

BACK INTO ENGLISH

Last night, after drinking, I lost my wallet when I left my grandma's house.

INTO JAPANESE

昨夜、お酒を飲んだ後、おばあちゃんの家を出るときに財布をなくしてしまいました。

BACK INTO ENGLISH

Last night, after drinking, I lost my wallet when I left my grandma's house.