It happens more often than you would think. You open the box, lay out all the parts, start assembling your new park bench, and then you realize one bolt or screw is nowhere to be found. Do not worry, you have several easy options.
First, double-check the packaging. Small hardware packs often get taped to cardboard flaps, hidden under folded panels, or trapped in the corners of the box. I have found missing screws inside the bottom of the box under a cardboard divider more times than I can count. If you have a parts list in the manual, check every bag against it before deciding something is truly missing.
If it is really not there, the next step is to identify exactly what you need. Look at the assembly manual for a hardware code like B7 or M6x40 and a short description. If there is no code, measure another matching bolt or screw from the same step. For bolts, you mainly need diameter, length, and thread pitch. A hardware store can match it if you bring an intact sample. For screws, length and gauge are usually enough.
Then contact the seller or manufacturer. Most companies will ship a replacement hardware pack free of charge. Have your order number, the model number, and the part number from the manual ready. A photo of the parts list or the empty hardware bag helps speed things up. This is usually the cleanest route because you will get the exact factory hardware.
If you do not want to wait for shipping, you can buy a replacement locally. Just make sure it is outdoor-grade. Stainless steel or galvanized bolts and coated deck screws are your friends. Avoid plain uncoated steel because it will rust and stain the wood after the first rain. Match the original size and length, and use a washer if the original had one. Do not force a longer bolt into a blind hole or use a thinner bolt that wobbles.
One thing I always tell people: do not assemble the bench with missing structural hardware and think it will be fine. A single missing bolt on a leg brace or seat support can make the whole bench unstable, and that is a safety risk. If the missing piece is structural, wait for the replacement or buy a proper match before using the bench. If it is purely cosmetic or a minor slat screw, you can often finish the bench and add the screw later without danger.
While you are at it, check every other bolt, nut, and screw in the kit. If one was missing, there may be another wrong piece or a stripped hole. Test-fit hardware before tightening everything. Tighten by hand first, then use the tool, and do not overdo it because outdoor wood and plastic parts can crack.
So in short: search the box carefully, identify the hardware, contact the seller for free replacement, or grab a matching outdoor-grade bolt or screw locally. It is an annoying start, but it is one of the easiest problems to fix on a park bench.