Yeah, Williams was actually the previous emergency catcher, and now it's Torreyes, but making Harper that and actually using him are two very different things. Wasn't Werth, a pretty valuable player (and a RF) in that role for a while too though? He had experience too of course.
They're probably gonna have to bring in a FA catcher if JT actually can't play for multiple day. If I understand it correctly none of the COVID guys can return for 10 full days because they had symptoms and tested positive. Testing negative earlier in that window isn't enough, you have to serve the quarantine period and then test negative at the end.
Hopefully Marchan - like Maton and Williams before him - can have a hot stretch even if it's not sustainable long-term. At this point there is no long-term.