Such topic frequently arrive that buyer has placed order by mistake. How funny…
Actually I don’t believe that an order can be create by mistake.
1.Because it is not a one click process.
2. Also need money for place an order. People think multiple time for any spent.
Important question : How much order value ?
Absolutely $5. because I have checked your gig. Basic price is $5.
( Because such mistaken buyer never buy suppose $500 gig by mistake)
Anyway, You may request to the buyer for not cancel order. $5 is not a big amount.
You will help them anytime for small work for this $5.