If the cement block is too heavy or to uneven for your vacuum to work, you can try this trick….(I used this method to remove my MAGLIGHT that my dumb-ass dropped down a sewer clean-out once.)
rent a small kitchen sink sized rooter snake and tie a large rag to the end of it securely so it cant come off.
Lower the snake and rag past the 3″ opening you said you have on the side of the cement block, then turn on the rooter machine for a brief time so that the rag spins around itself and doubles or triples its diameter so that it becomes the same diameter of the well pipe below the cement.
then slowly pull the snake out by hand.
I know it sounds kinda funny but I still have my MAGLIGHT!