It's hard to say exactly why someone might suddenly gain a number of 30 instant followers online. It is possible someone else bought some subscribers for your IG account, as there is no password needed to buy. However, it could also be due to a viral piece of content, or any recent press you may have had for your business or brand. An increase in legit, 30 high-quality fans is always a good thing, and you might consider building on your success by purchasing more fans.