In general I am an outgoing person and tend to meet a lot of new people. 
I work at a software company and some of the people I meet in public are software engineers. I am a senior engineer and architect and currently run a team at my company.

Our company, like most software companies, is most definitely short on good engineers and the other day on the train I met two young people in their last few months of university who were very interested in finding work. I know that we are specifically looking for this exact profile. They asked me for my card and sent in CVs the next day.

I forwarded them to HR, saying something like "I was waiting for the train and met some engineers. Here are their resumes. Are these interesting for you?"

I got this message back from HR and am debating with myself what to think about it: "What a nice place to recruit new people =)".

I have a feeling this is a passive aggressive note implying I should feel bad about promoting the company. In general I am planning to ignore the comment (at least, not respond by email) but it makes me wonder how should I interpret this and if I should do something differently? 

The two people I met, in my mind, have excellent profiles. Looking at the one CV, it's very solid. Maybe I am too open-minded, but is it reasonable to consider them, or is it a black mark on me or the candidate just because I met them in a two minute conversation while switching trains instead of a two minute conversation on a recruitment day? Why would this be worse than applying via our public website?