Non intersecting paths in a graph
Nope, this algorithm doesn't work.  It is possible to find an explicit counterexample.  Since it sounds like this is an exercise you're doing to learn algorithms, I won't spoil the exercise for you, but I'll just give you some hints that may help you find a counter example.


Start with a graph containing just a single path from $s$ to $t$, and nothing else.  Make it a fairly short path, say, 5 edges long.
Introduce a long path from $s$ to $t$ (say, 10 edges long or so) that coincides with the short path for a brief while then diverges.
Now introduce a second long path from $s$ to $t$ with two properties: (a) it is edge-disjoint with the first long path, (b) it has at least one edge in common with the short path.


Finding a counterexample is a little tricky, but draw it out and try some ideas, and I bet you'll be able to figure out.



Your approach doesn't work, but there are other algorithms to solve this problem.  However, they're fairly complicated: more complicated than your could reasonably be expected to discover on your own.  Assuming this is a homework/exercise, I can't just can't believe your teacher would assign you an exercise that requires you to independently re-discover those algorithms -- so there must be some other trick or background information available to you.  You might check in with your teacher.

The other algorithms use the following idea: Look for a "funnel" edge $e$ such that all paths from $s$ to $t$ "funnel through" the edge $e$ (i.e., all paths from $s$ to $t$ must include the edge $e$).  If you find such an edge, obviously there is no pair of edge-disjoint paths from $s$ to $t$.  If you don't find such an edge, then it turns out that there's guaranteed to exist two edge-disjoint paths from $s$ to $t$.  Proving this is tricky, though, as is devising an efficient algorithm to rapidly test for the existence of such an edge.



Since you asked for references, this problem is solved by the following characterization: there are two vertex-disjoint paths from $s$ and $t$ if and only if $s,t$ are part of the same biconnected component.  There are fancy algorithms to decompose a graph into biconnected components in linear time.  Similarly, there are two edge-disjoint paths from $s$ and $t$ if and only if $s,t$ are part of the same 2-edge-connected component.  There are fancy algorithms to decompose a graph into 2-edge-connected components in linear time (or, you can reduce to the problem of computing biconnected components by computing a new graph that swaps vertices and edges).

So, an efficient answer to your question is: decompose the graph into 2-edge-connected components (using the algorithms mentioned in the previous paragraph), then test whether $s$ and $t$ are in the same component.

For more, see e.g., https://en.wikipedia.org/wiki/Biconnected_component and  https://en.wikipedia.org/wiki/Bridge_%28graph_theory%29 and https://en.wikipedia.org/wiki/K-edge-connected_graph.