To be fair, the article does mention textual evidence of contact. It just say the ring is a rare archaeological evidence, which is correct.
From "Silver Economy In The Viking Age" edited by James Graham-Campbell, Gareth Williams:
"It is also relevant to note that, both in Denmark itself, and more widely in Scandinavia, coin finds from the ninth and tenth centuries are dominated by Islamic dirhams and their Khazar, Bulghar and possibly Russian imitations, rather than by native Danish coins or their Frankish models (Hovén 1981; Kromann 1990; Jensen and Kromann 1998; Talvio 1998)."