If you were having trouble finding 怖い by searching for “I’m scared”, it might be because 怖い literally means “scary”. It just implies “I’m scared” and that is often the most natural way to translate it into English.
It was like a 50/50, because I couldn’t hear the わ – I just kept trying variations of こえ and こい. Then searching backwards on “apprehensive,” “scared,” “fear” turned up nothing.
I remember having a similar problem when I watched The Devil is a Part Timer. The word “面倒くさい” (めんどうくさい) is used quite often and I wanted to find out what it was they were saying, but I thought what they were saying started with an ‘r’ and I didn’t know how long the vowels were, so I eventually googled something like “Japanese word that means annoying and sounds like rendokusai” That got me to the answer. I think if you are having trouble with something, there are good chances others have also had that trouble and have posted something about it.
Possibly just a lot more listening practice could help you too.
Hmm. Not as entirely successful, but with digging in the results I got there. Sometimes I forget that google is really good at weird sentence questions like that – I mostly don’t use it in that way though. I think part of it was that it was such a short clip + sentence that posting it here was bound to get me something obvious fast.