Bot Stopped But Still Gaining

Instagram Veterans,

I had been using spam accs to promote my main for about a month. With the recent IG attack, it has forced me to stop. I just post an image a day with no hashtags on my main to keep active. To my surprise, I am still getting likes from non followers and some are following me. I've double checked to see if they are my followers and they aren't.

My question. How are they finding my photos if I am not using hashtags? Are they going through their following list and following their followers which are following me?

I am at 15K btw.

maybe because your posts gained much likes and are popular so non-followers can see it too? I don't know about mobile app, but in InstaPic (win 8 App) there is a popular section and I can see the posts of people I don't even follow, but I see em because they are popular posts.