I could swear that I commented yesterday on Where can I download Safari for Windows?, but I am not seeing it now.
Assuming it has been deleted, is there anywhere to access it, and/or see the reason for it's deletion?
Yes, a moderator removed the comment because it wasn't related to any question or answer particularly and was rather discussion about who might have downvoted an answer. No-one, not even moderators, can see who voted for who (unless there is a pattern of vote abuse that is picked up by the system and alerted to us) and questioning a user on their voting isn't considered appropriate.
Unlike for questions, reasons are not stored for edits and deletion of comments so there is nothing to see. As mentioned by @Mat, only moderators can see deleted comments.