Wanna preface this by saying I'm basically bilingual in terms of frequency of use: use Germany all day every day at work but English is my mother tongue. I think sometimes using two languages this much can mess with your head when it comes to remembering random words in each. Got home from work one day, had a convo with someone where I needed to mention someone's grandfather, but couldn't remember the word grandfather itself. My brain dug real hard to try and think of wtf the word was and then finally spit out: "Oh yeah, that's his Superdad."
I'm bilingual as well, Finnish is my mother to tongue but I'm also fluent in English. I constantly forget words, only able to remember them in the language I am not using... one time I forgot the English word for towel. Of all things, *towel* eluded me
I am trilingual. I forgot how to say no in Spanish. So I said it in Hebrew, because I had just spent 6 months in Israel. No in Spanish is no. The parent I was speaking to was clearly confused, but said nothing.