sounds to me like that might be a problem with the memory card not the camera. if you have a different memory card, try using it for a while and if the problem persists then its the camera. you can call canon support, they’re usually very helpful- i once called them and the lady told me about a promotion that i had never heard of, where i could mail in my defective sd600 and she would send me a new camera for half the price. i dont know if that works on the sd750 series but you should definitely find out since the 750 is an older model.
in terms of recovering the pictures, if they are ‘stuck’ on the memory card, you can send it to a data recovery place and see if they can get it out. i know one in florida that i use for business related data recovery its called LC Tech the number is 866-603-2195 and ask for Eric. or go to lctech.com.