The pilot reported that, prior to a local flight, he placed the airplane's wing and canopy covers and his small dog in the baggage compartment. During the initial climb, after retracting the landing gear, the cockpit canopy, which tips forward for entry into the cockpit, came unlatched and opened to about a 45° angle. He attempted to close and re-latch the canopy to no avail and decided to return to the departure airport. Subsequently, after extending the landing gear on final, the airplane lost speed and the descent rate increased. He applied full power, but the airplane landed hard and short of the runway, and the landing gear collapsed. The pilot reported that the airplane had an after market drop down step kit that had been uninstalled; however, during the kit removal, the step mechanism had been removed but the brackets that extended into the baggage compartment had been overlooked. The brackets were attached to the canopy latching mechanism, and he believed his dog accidently hit the protruding brackets and inadvertently opened the canopy in flight. The airplane sustained substantial damage to the center wing spar. The pilot reported that prior to the canopy opening, there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation.