Collar?? Tags of any kind? If U have pics print out some lost cat fliers and put them up all around the neighborhood. Maybe even go door-to-door w/the fliers.
We went thru this too when we moved in Nov. Didn't realize the garage went directly under/into the foundation of the house and there was a hole to the outside. Pesky got out the first night right after we moved. Luckily she was stil wearing the tags from my sister's in Seattle. The neighbor called the number and my sister called me at work.
The "finder" was only two houses downbut it took us 2 days to get Pesky back.
We'll keep our fingers crossed and prayers floating for you.I KNOW how worried you both are!