Hi Will GetGC,
I am no guru, but it happened 2 or 3 times for us that VSC either sent no notice at all or that USPS screwed up, but for "minor" applications than I-140. If he/she has used a personal check (I think you can use personal check for up to 200 USD), then he/she can track online or call them when he/she gets back your check, because they write the receipt number on the back side of the check. I use my online bank account to "track" whether they have received applications based on the cashing of the checks and use money orders only it I have to. They are more reliable cashing checks than sending out receipt notices...
Our I-140 receipt notices arrived 1-2 weeks after sending the applications (VSC I-140 EB1EA and NIW one month ago).
Hope this helps a little...