on my wrong side

What's a wrong side?

I couldn't see his motorcycle both from my rear vision and side mirrors.

You seem inattentive. The motorcyclist didn't "sneak" into a spot, he simply minded his own business and parked. You didn't even notice a motorcycle park behind you while you were moving things around inside your car? I'm sorry, but you're simply inattentive.

many motorcyclists drive from their perspective and not that of four-wheeled driver's

This statement strikes me as extremely ironic.

"What's a wrong side?"

You are obviously a motorcyclist.

And so it's OK for motorcyclists to disobey road rules on a public street and be inconsiderate to others? Why would a car driver expect to find a motorcycle illegally parked between two legally parked cars with only several inches between the car and the motorcycle?

If you drive a car, I'll bet London to a brick you don't get out and back into your vehicle just the moment before you drive off. Show me someone who does and I'll retort "by golly you've found the mystical unicorn".

BTW, being in a safely parked car with the ignition switched off and doing something doesn't count or constitute as being inattentive as it would after the ignition is switched on and the motor running. Despite what you say I'm particularly attentive at what's at my rear (even after checking it's why I always back up at a snail's pace). The street in question is very noisy and pedestrians regularly flit between parked cars—it's all the more reason. Motorcycles can't be heard above the street noise, and when riders park tightly between two cars they'll wheel them in with motor off (but you'd already know that).

It's your comment that's ironic. I'd also maintain that road statistics support the notion that such attitudes have to change before they'll improve for the better.