The issue of being injured by the syringe is serious. You are understandably and justifiably upset.

It's hard not to blame someone or something for this happening to you, but I think it's unfair to blame Sunnyside.
It could have fallen from a tourist's bag or pocket in addition to any other number of reasons it was there.

If you are not happy with the response you got from Robert, that is an issue between him and you. Not something to be hashed out on a public forum.