A hypothesis is unfalsifiable when by its very nature it cannot be disproven by any amount of evidence. This idea is important when making any kind of claim and when verifying claims. A scientific claim that cannot be tested does not need to be.
"Seek and you shall find."
This statement cannot be proven wrong because the seeker will either find what they are looking for or they will keep looking. The statement can be right, but it can never be wrong. Even if what the seeker is looking for does not exist, they cannot prove this with complete certainty because there is an infinite amount of places to look. To make this into a falsifiable hypothesis, one must make the test required to prove or disprove this statement possible. For example, restrict the search area to a finite one: "Seek in the physics building and you shall find." Alternatively, restrict the amount of time to a finite amount: "Seek for 50 years and you shall find."
"This vault can be broken into."
In order to prove this statement wrong, one would have to try to break into it for an infinite amount of time, which is impossible. To make this falsifiable, one can just limit the amount of time: "This vault can be broken into in 10 hours."