My yahoo mail won’t show deleted email on my Iphone

I can see the deleted emails on the lap top but not my phone! I know it is hard to believe but I have on occasion deleted an email I wanted to keep. I can not go to the delete folder and return it to the inbox because both my delete and spam folder are always empty when I view them on my phone!! I must of changed a setting sometime ago but I have no clue how or where to get it to work again! Any help you can give me will be very welcome 😍