"If it is indeed Him."
That's always the question, isn't it?
To me, there is compelling evidence about Lourdes - all of those thousands of medical files.
On the other hand, when Mary starts showing up in dried cheese sandwiches on e-Bay, I start to have crippling doubts. I suppose even that COULD be God's work, but if it is, I'm afraid He's not going to convince me that way...well, unless I was the one eating the sandwich, I suppose...
I will be pretty blunt here: If a miracle has no practical value (Healing, opportunity, deflecting a meteor), it is not of the God of the Bible.
Can you name one miracle from the Word of God that had no practical purpose besides, arguably, the fig tree? If you can, I will reconsider my position.
BTW, I have experienced thre bona-fide miracles in my life, so I do believe they exist.