Bryan,
If I understand your intent, you want your pages indexed. I see that your site has 5 pages indexed (/, /help, /influencers, /wholesale, /co-brand). And that you have some other pages (e.g. /donations), which are not indexed, but these have "noindex" tags explicitly in their HEAD sections.
Not having a robots.txt file is equal to having a robots.txt file with a directive to allow crawling of all pages. This is per http://www.robotstxt.org/orig.html, where they say "The presence of an empty "/robots.txt" file has no explicit associated semantics, it will be treated as if it was not present, i.e. all robots will consider themselves welcome."
So, if you have no robots.txt file, the search engine will feel free to crawl everything it discovers, and then whether or not it indexes those pages will be guided by presence or absence of NOINDEX tags in your HEAD sections. From a quick browse of your site and its indexed pages, this seems to be working properly.
Note that I'm referencing a distinction between "crawling" and "indexing". The robots.txt file provides directives for crawling (i.e. access discovered pages, and discovering pages linked to those). Whereas the meta robots tags in the head provide directives for indexing (i.e. including the discovered pages in search index and displaying those as results to searchers). And in this context, absence of a robots.txt file simply allows the search engine to crawl all of your content, discover all linked pages, and then rely on meta robots directives in those pages for any guidance on whether or not to index those pages it finds.
As for a sitemap, while they are helpful for monitoring indexation, and also provide help to search engines to discover all desired pages, in your case it doesn't look especially necessary. Again, I only took a quick look, but it seems you have your key pages all linked from your home page, and you have meta directives in pages you wish to keep out of the index. And you have a very small number of pages. So, it looks like you are meeting your crawl and indexation desires.