Hume famously said,
That no testimony is sufficient to establish a miracle, unless the testimony be of such a kind, that its falsehood would be more miraculous, than the fact, which it endeavours to establish: And even in that case, there is a mutual destruction of arguments, and the superior only gives us an assurance suitable to that degree of force, which remains, after deducting the inferior.
In this context, Hume refers to miracles as violations of law. This could include for example someone rising from the dead or the sea being split into two. However, many religious people often see certain events in their life, such as prophetic dreams, improbable coincidences, potentially meaningful signs, etc. as evidence for God, events that they themselves acknowledge as possible under natural law. It is often what underpins their belief. Fine tuning arguments also fall into this category since theists don’t argue that it is impossible for constants to be fine tuned without god, but rather for it to be really unlikely.
Now, can one make a Humean argument against these sorts of evidence by the simple recognition that we have never observed a non human designer design anything? In other words, no matter what event we come across, as long as it is possible under natural law which itself acts as prima facie evidence, blind natural laws explaining that event must be more probable than god designing something for the simple fact that we have never observed the latter.
Would this kind of argument follow?
Side note: I suppose a theist could simply deny that there is any prior evidence of anything being caused by blind natural laws and say that everything is designed by god. This is fine but this then takes away the importance of their argument. If everything must be designed, then something like the fine tuning argument loses its power, since even if the constants did not result in life, it would support design just as much as constants that do result in life