That is simply not so. I have your uniquely Catholic doctrine. The Didachist is not a Sola Scriptura Christian. He alludes to several, several ideas that are simply NOT FOUND in scripture. Here’s an uncomplete list:
(1) Didache 2:2 - Abortion is forbidden. This idea may be implicitly found throughout Scripture, but it is never found explicitly in Scripure, as it is here.
(2) Didache 4:6 - Almsgiving pays a “ransom” for sins. Why would the author even mention this if Jesus paid the full price for sins on the cross? The answer can only point to Purgatory.
(3) Didache 7:1 - The idea that baptism should take place preferably in living (running) water.
(4) Didache 7:3 - We can baptize by pouring water instead of full immersion.
(5) Didache 7:4 - Those baptizing and being baptized should fast before the baptism itself
(6) Didache 8:2 - The Our Father contains the phrase, “For yours is the power and the glory forever,” even though Jesus never taught us to pray that.
(7) Didache 9-10 - The prayers for Communion are not found anywhere in Scripture.
(8) Didache 9:5 - The idea that only baptized Christians can partake of holy communion.
(9) Didache 14:3 The author links the prophecy about sacrifice from Malachi 1:11, 14 with holy communion, asking that Christians reconcile so that their “sacrifice” may be pure.
There you have it friends. The Didachist was no Sola Scriptura Protestant.