Is there another diagnostic test that other than an MRI that would show a rupture?

Ultrasound and CT imaging can also be used to detect implant rupture. Ultrasound is an excellent tool for detecting implant rupture that is non-invasive and radiation-free. CT is generally not the first test of choice given its lower sensitivity and specificity. (Silicone looks similar to other tissues on a CT image, making something called extra-capsular rupture more difficult to detect.)
Something called capsular contracture can cause implants to sit higher on the chest and cause an asymmetry between the sides. This can occur with and without rupture of the breast implant.

Yes, both MRI and HFUS (high frequency ultrasound) are good techniques to determine if your implants are intact. However, it is always best to go to your surgeon first so that he/she can examine you and decide which is the best course of action. Your surgeon can also give you an idea of why the left implant is higher and more hard, since many times this is not due to rupture. Best of luck!