In the Slack API I am trying to get the individual Slack IM object that a file is shared on, but from the looks of the im methods, it looks like you can only retrieve im objects using im.list, which lists all of the IMs for a user (https://api.slack.com/methods/im.list). Is there any way to query for just one IM?
You don't today. But IM List return an Array you can make this with a for boucle.