Keep up the communication with him and find out if he has tracking numbers. If not, ask him specifically what he did when he sent them and how he sent them then check out his story with your local Post Office or UPS and see if what he says is possible. You're in PA, right? That may be an area that is a bit of a hotzone right now so perhaps there is some local hangup. Clear all the possibilities first but definitely keep up the communication. Ask him what he feels is fair in this situation regarding him having your knives and you not receiving yours. Did you discuss this before doing the deal? If so, and you came up with a plan then you must stick with that. Otherwise you will need to come up with an agreement between each other. Also, check out his name and reputation in G, B, and U to get some background so you can further determine if you are possibly getting screwed or if he was previously a straight shooter.
Bottom line, use this place as a last resort and only when you've exhausted ALL other avenues before posting his name and information. Coming here for information or advice is great but be sure not to jump the gun.
Hopefully all will work out in the end so keep this post up to date as things develop and you'll get more advice along the way.
Best of luck and I hope you get your blade!
Shawn