Trust me, working as an accountant i'd say it's not excluded that it wasn't by mistake ;)

Since we switched our program at work, our costumers even use frequently our VAT id as invoice number, or they make up completely random invoice numbers, change the invoice number format (like instead of 2026-######### they write ######### 2026), others fail to set the comma correctly and pay 12.000€ for an invoice of 120€ and the list goes on... So trust me, when i say the BTC could've been sent by mistake to that address. And yes, even 5 times xD