I have never encountered any evidence that would make me presume else wise
And so you take all accounts of miracles when someone tells you of them as false, as you require your own first person experience to admit not even the actuality of something, but even the potentiality of it?
Christians don't become Christians because they see miracles happen. They see miracles happen because they are Christians.
In fact, Craig Keener has pointed out that miracles are the most common among the mission field, areas with limited prior exposure to Christianity. Sources like the China Christian Council shows a large percent of Christian converts (up to 90 pct in rural areas) in China cite a healed illness as a reason for conversion*to Christianity*. So it is clear that God, among other means, provides clear testimony to the gospel to people who have never been exposed to the faith before through miraculous healing.
Hm...I wonder if the issue here could be the preexisting superstition and undereducation of rural China being contextualized in a new light, not sickness magically disappearing. That's some poorly founded logic.