Liquid in the cylinder can indeed bend a rod, and who knows what other damage may be caused. But this is typically when liquid is in the cylinder and the other cylinders fire, and then it may even take revving up the engine to get enough energy to cause major damage. If it was ONLY the starter which hit this liquid, and the engine didn't fire, you probably did not sustain any damage.
You are correct in concern over connecting rods. The rod is by far the most stressed piece of the engine.
Is everything running okay now?
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in