All may not be lost. When I searched for information on .sif files, I came up with a number of different definitions, including Andor Scan Information File (there are at least two TMW File Exchange entries for those), and Cytoscape Simple Interaction Format. (They are also Windows Setup Information Files, but those likely aren't the ones you are interested in.)
What generated your .sif file, and what does it contain? How many rows and columns should it have? If it is supposed to be a matrix rather than a vector, it may be possible to get the time data (if there is a time vector in the matrix) by doing reshape on it.
