A lot of “doing the right thing” is called: due diligence.
This is where you – and, better yet, your qualified attorney – “diligently” attempt to discover whether there are any IP-rights issues, and document in writing(!) exactly what they did and when they did it. And, that they concluded that what they were doing was legal “and here’s why.” Clearly document that you did this before using the materials. If any possible rights-holder could have been queried, document that you did so “at this address.” Or, “at 11:23 AM on X date, I called ‘this’ number and spoke to Y, who said …”
Be precise, be pro-active, and get it all on paper.
If there are any proprietary markings that could be included, include them all, along with (say …) “Fair Use,” or “Used By Permission.” There is an obscure but very important legal doctrine called the Doctrine of Laches which comes into play here, and it’s the vexation of every IP-rights holder (including you).
Of course … "Bam! Now, someone hits you with a “cease and desist” order. You have now properly set yourself up for an innocent infringement defense, and possibly to defeat the order itself.
About twenty years ago, I started writing a software product – still on-sale to this day – which would include some technology, and upon reading their license agreement I saw a gray area. So, I found the address of the company’s legal department and, before incorporating the technology, I wrote them a letter, described exactly what I intended to do, and asked them to clarify their position by return post. After picking themselves up off the floor in surprise, they quickly and politely sent their reply, signed by an appropriate company officer, and added, “thanks for asking!” Of course I still have both letters in my file. “Due diligence.”
"It never hurts to 'just ask."