Parsing Email Subject Then Updating Item

Hello all,

I've created a mini-service desk application in SharePoint 2013 with Nintex Workflow 2013. One of the workflows parses the subject of an incoming email to look for a ticket number, and if it finds a ticket number, updates the ticket number field automatically. I can get this workflow to trigger when an item is modified, but I can't get it to trigger when an item is created.

After searching these boards, I discovered that this is by design. Workflows won't execute automatically on a system-created item.

My next step was to create a site workflow to do the same thing. So far, I've been unsuccessful, which I assume is because I've never worked with collection variables before. Here's what I'm doing:

1. Query list for any items where the ticket number field is blank and store those items' ID numbers in a collection variable
2. For each item in that collection variable, store the ID in a single line of text variable
   1. Query list for an item that matches the ID variable and store the Email Subject in a single line of text variable
   2. RegEx that variable to extract the ticket number, store that ticket number in a collection variable
   3. Collection operation to get the ticket number out of the collection and store in a single line of text variable
   4. Update Item where the ID matches the previously store single line of text variable, changing the ticket number field to the ticket number variable

Any idea where I could be going wrong here? I'd appreciate a solution to the first problem, if there is one, because that's cleaner, but I'm open to using the site workflow on a regular schedule if I have to do that.