You won't like this answer, but you should not seek compensation from your workplace. Consider if you drove a car and it got dinged in the parking lot. Would you expect to have your employer repair the damage? (In case you're unsure, the answer is no.) This is made even worse by parking your bike in a spot not designed or designated for bike parking, and that you know cars frequently get close to. I understand the desire for convenience, and nobody appreciates having their property damaged, but there is no way your employer will pay for it. You will seem whiny and entitled if you even ask. Don't do it.
Your only recourse to recoup the damages is to find the person that hit your bike. You can try filing a police report, but if the costs are minimal, they likely won't bother to pursue it. If there is a camera at the front of the building, you could ask security to review it and get you a plate number. If it's a really small company, you could try putting up a notice somewhere asking the person to come forward. You have to be really careful how you word it to not come across as passive aggressive, though. I personally wouldn't bother unless the costs were really high, as it's unlikely anyone will 'fess up to it.
To prevent this happening in the future, I suggest you request a designated, safe, and relatively convenient place to park your bike. This is entirely reasonable, especially if they provide parking for cars. Tell your management that you tried to find an existing place to lock up your bike, but your bike got damaged there, and you'd like a safer place to put it in the future.
If they don't agree, then you are stuck with the same preventative measure that car owners have to use: park your vehicle somewhere that cars are unlikely to get close enough to damage it. That generally comes at a convenience cost, so you will have to decide if the trade-off is worth it or not.